[PATCH v6 00/32] Support multiple checkouts

[PATCH v6 00/32] Support multiple checkouts

[Nguyễn Thái Ngọc Duy]

This is basically a reroll from what was parked on 'pu' with two
new patches at the end: one to not share info/sparse-checkout
across worktrees, and one to allow 'checkout --to` from a bare
repository.

I cherry-picked two patches from jk/xstrfmt (on next) because they
result in non-trivial conflicts. When this series is merged with
jk/xstrfmt, you still get conflicts in environment.c, but you can just
pick up my changes and drop Jeff's.

Dennis Kaarsemaker (1):
  checkout: don't require a work tree when checking out into a new one

Jeff King (2):
  setup_git_env: use git_pathdup instead of xmalloc + sprintf
  setup_git_env(): introduce git_path_from_env() helper

Nguyễn Thái Ngọc Duy (29):
  path.c: make get_pathname() return strbuf instead of static buffer
  path.c: make get_pathname() call sites return const char *
  git_snpath(): retire and replace with strbuf_git_path()
  path.c: rename vsnpath() to do_git_path()
  path.c: group git_path(), git_pathdup() and strbuf_git_path() together
  git_path(): be aware of file relocation in $GIT_DIR
  *.sh: respect $GIT_INDEX_FILE
  reflog: avoid constructing .lock path with git_path
  fast-import: use git_path() for accessing .git dir instead of get_git_dir()
  commit: use SEQ_DIR instead of hardcoding "sequencer"
  $GIT_COMMON_DIR: a new environment variable
  git-sh-setup.sh: use rev-parse --git-path to get $GIT_DIR/objects
  *.sh: avoid hardcoding $GIT_DIR/hooks/...
  git-stash: avoid hardcoding $GIT_DIR/logs/....
  setup.c: convert is_git_directory() to use strbuf
  setup.c: detect $GIT_COMMON_DIR in is_git_directory()
  setup.c: convert check_repository_format_gently to use strbuf
  setup.c: detect $GIT_COMMON_DIR check_repository_format_gently()
  setup.c: support multi-checkout repo setup
  wrapper.c: wrapper to open a file, fprintf then close
  use new wrapper write_file() for simple file writing
  checkout: support checking out into a new working directory
  checkout: clean up half-prepared directories in --to mode
  checkout: detach if the branch is already checked out elsewhere
  prune: strategies for linked checkouts
  gc: style change -- no SP before closing bracket
  gc: support prune --repos
  count-objects: report unused files in $GIT_DIR/repos/...
  git_path(): keep "info/sparse-checkout" per work-tree

 Documentation/config.txt               |   9 ++
 Documentation/git-checkout.txt         |  34 +++++
 Documentation/git-prune.txt            |   3 +
 Documentation/git-rev-parse.txt        |  10 ++
 Documentation/git.txt                  |   9 ++
 Documentation/gitrepository-layout.txt |  75 ++++++++--
 builtin/branch.c                       |   4 +-
 builtin/checkout.c                     | 248 ++++++++++++++++++++++++++++++++-
 builtin/clone.c                        |   9 +-
 builtin/commit.c                       |   2 +-
 builtin/count-objects.c                |   4 +-
 builtin/fetch.c                        |   5 +-
 builtin/fsck.c                         |   4 +-
 builtin/gc.c                           |  21 ++-
 builtin/init-db.c                      |   7 +-
 builtin/prune.c                        |  74 ++++++++++
 builtin/receive-pack.c                 |   2 +-
 builtin/reflog.c                       |   2 +-
 builtin/remote.c                       |   2 +-
 builtin/repack.c                       |   8 +-
 builtin/rev-parse.c                    |  11 ++
 cache.h                                |  17 ++-
 daemon.c                               |  11 +-
 environment.c                          |  45 ++++--
 fast-import.c                          |   7 +-
 git-am.sh                              |  22 +--
 git-pull.sh                            |   2 +-
 git-rebase--interactive.sh             |   6 +-
 git-rebase--merge.sh                   |   6 +-
 git-rebase.sh                          |   4 +-
 git-sh-setup.sh                        |   2 +-
 git-stash.sh                           |   6 +-
 git.c                                  |   2 +-
 notes-merge.c                          |   6 +-
 path.c                                 | 234 +++++++++++++++++++++----------
 refs.c                                 |  86 +++++++-----
 refs.h                                 |   2 +-
 run-command.c                          |   4 +-
 run-command.h                          |   2 +-
 setup.c                                | 124 +++++++++++++----
 sha1_file.c                            |   2 +-
 submodule.c                            |   9 +-
 t/t0060-path-utils.sh                  |  35 +++++
 t/t1501-worktree.sh                    |  76 ++++++++++
 t/t1510-repo-setup.sh                  |   1 +
 t/t2025-checkout-to.sh (new +x)        |  72 ++++++++++
 templates/hooks--applypatch-msg.sample |   4 +-
 templates/hooks--pre-applypatch.sample |   4 +-
 trace.c                                |   1 +
 transport.c                            |   8 +-
 wrapper.c                              |  31 +++++
 51 files changed, 1109 insertions(+), 265 deletions(-)
 create mode 100755 t/t2025-checkout-to.sh

-- 
1.9.1.346.ga2b5940

[PATCH v6 01/32] path.c: make get_pathname() return strbuf instead of static buffer

[Nguyễn Thái Ngọc Duy]

We've been avoiding PATH_MAX whenever possible. This patch makes
get_pathname() return a strbuf and updates the callers to take
advantage of this. The code is simplified as we no longer need to
worry about buffer overflow.

vsnpath() behavior is changed slightly: previously it always clears
the buffer before writing, now it just appends. Fortunately this is a
static function and all of its callers prepare the buffer properly:
git_path() gets the buffer from get_pathname() which resets the
buffer, the remaining call sites start with STRBUF_INIT'd buffer.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 path.c | 120 ++++++++++++++++++++++++++++-------------------------------------
 1 file changed, 51 insertions(+), 69 deletions(-)

diff --git a/path.c b/path.c
index bc804a3..42ef3af 100644
--- a/path.c
+++ b/path.c
@@ -16,11 +16,15 @@ static int get_st_mode_bits(const char *path, int *mode)
 
 static char bad_path[] = "/bad-path/";
 
-static char *get_pathname(void)
+static struct strbuf *get_pathname(void)
 {
-	static char pathname_array[4][PATH_MAX];
+	static struct strbuf pathname_array[4] = {
+		STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
+	};
 	static int index;
-	return pathname_array[3 & ++index];
+	struct strbuf *sb = &pathname_array[3 & ++index];
+	strbuf_reset(sb);
+	return sb;
 }
 
 static char *cleanup_path(char *path)
@@ -34,6 +38,13 @@ static char *cleanup_path(char *path)
 	return path;
 }
 
+static void strbuf_cleanup_path(struct strbuf *sb)
+{
+	char *path = cleanup_path(sb->buf);
+	if (path > sb->buf)
+		strbuf_remove(sb, 0, path - sb->buf);
+}
+
 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
 {
 	va_list args;
@@ -49,85 +60,70 @@ char *mksnpath(char *buf, size_t n, const char *fmt, ...)
 	return cleanup_path(buf);
 }
 
-static char *vsnpath(char *buf, size_t n, const char *fmt, va_list args)
+static void vsnpath(struct strbuf *buf, const char *fmt, va_list args)
 {
 	const char *git_dir = get_git_dir();
-	size_t len;
-
-	len = strlen(git_dir);
-	if (n < len + 1)
-		goto bad;
-	memcpy(buf, git_dir, len);
-	if (len && !is_dir_sep(git_dir[len-1]))
-		buf[len++] = '/';
-	len += vsnprintf(buf + len, n - len, fmt, args);
-	if (len >= n)
-		goto bad;
-	return cleanup_path(buf);
-bad:
-	strlcpy(buf, bad_path, n);
-	return buf;
+	strbuf_addstr(buf, git_dir);
+	if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
+		strbuf_addch(buf, '/');
+	strbuf_vaddf(buf, fmt, args);
+	strbuf_cleanup_path(buf);
 }
 
 char *git_snpath(char *buf, size_t n, const char *fmt, ...)
 {
-	char *ret;
+	struct strbuf sb = STRBUF_INIT;
 	va_list args;
 	va_start(args, fmt);
-	ret = vsnpath(buf, n, fmt, args);
+	vsnpath(&sb, fmt, args);
 	va_end(args);
-	return ret;
+	if (sb.len >= n)
+		strlcpy(buf, bad_path, n);
+	else
+		memcpy(buf, sb.buf, sb.len + 1);
+	strbuf_release(&sb);
+	return buf;
 }
 
 char *git_pathdup(const char *fmt, ...)
 {
-	char path[PATH_MAX], *ret;
+	struct strbuf path = STRBUF_INIT;
 	va_list args;
 	va_start(args, fmt);
-	ret = vsnpath(path, sizeof(path), fmt, args);
+	vsnpath(&path, fmt, args);
 	va_end(args);
-	return xstrdup(ret);
+	return strbuf_detach(&path, NULL);
 }
 
 char *mkpathdup(const char *fmt, ...)
 {
-	char *path;
 	struct strbuf sb = STRBUF_INIT;
 	va_list args;
-
 	va_start(args, fmt);
 	strbuf_vaddf(&sb, fmt, args);
 	va_end(args);
-	path = xstrdup(cleanup_path(sb.buf));
-
-	strbuf_release(&sb);
-	return path;
+	strbuf_cleanup_path(&sb);
+	return strbuf_detach(&sb, NULL);
 }
 
 char *mkpath(const char *fmt, ...)
 {
 	va_list args;
-	unsigned len;
-	char *pathname = get_pathname();
-
+	struct strbuf *pathname = get_pathname();
 	va_start(args, fmt);
-	len = vsnprintf(pathname, PATH_MAX, fmt, args);
+	strbuf_vaddf(pathname, fmt, args);
 	va_end(args);
-	if (len >= PATH_MAX)
-		return bad_path;
-	return cleanup_path(pathname);
+	return cleanup_path(pathname->buf);
 }
 
 char *git_path(const char *fmt, ...)
 {
-	char *pathname = get_pathname();
+	struct strbuf *pathname = get_pathname();
 	va_list args;
-	char *ret;
-
 	va_start(args, fmt);
-	ret = vsnpath(pathname, PATH_MAX, fmt, args);
+	vsnpath(pathname, fmt, args);
 	va_end(args);
-	return ret;
+	return pathname->buf;
 }
 
 void home_config_paths(char **global, char **xdg, char *file)
@@ -158,41 +154,27 @@ void home_config_paths(char **global, char **xdg, char *file)
 
 char *git_path_submodule(const char *path, const char *fmt, ...)
 {
-	char *pathname = get_pathname();
-	struct strbuf buf = STRBUF_INIT;
+	struct strbuf *buf = get_pathname();
 	const char *git_dir;
 	va_list args;
-	unsigned len;
-
-	len = strlen(path);
-	if (len > PATH_MAX-100)
-		return bad_path;
 
-	strbuf_addstr(&buf, path);
-	if (len && path[len-1] != '/')
-		strbuf_addch(&buf, '/');
-	strbuf_addstr(&buf, ".git");
+	strbuf_addstr(buf, path);
+	if (buf->len && buf->buf[buf->len - 1] != '/')
+		strbuf_addch(buf, '/');
+	strbuf_addstr(buf, ".git");
 
-	git_dir = read_gitfile(buf.buf);
+	git_dir = read_gitfile(buf->buf);
 	if (git_dir) {
-		strbuf_reset(&buf);
-		strbuf_addstr(&buf, git_dir);
+		strbuf_reset(buf);
+		strbuf_addstr(buf, git_dir);
 	}
-	strbuf_addch(&buf, '/');
-
-	if (buf.len >= PATH_MAX)
-		return bad_path;
-	memcpy(pathname, buf.buf, buf.len + 1);
-
-	strbuf_release(&buf);
-	len = strlen(pathname);
+	strbuf_addch(buf, '/');
 
 	va_start(args, fmt);
-	len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
+	strbuf_vaddf(buf, fmt, args);
 	va_end(args);
-	if (len >= PATH_MAX)
-		return bad_path;
-	return cleanup_path(pathname);
+	strbuf_cleanup_path(buf);
+	return buf->buf;
 }
 
 int validate_headref(const char *path)
-- 
1.9.1.346.ga2b5940

[PATCH v6 02/32] path.c: make get_pathname() call sites return const char *

[Nguyễn Thái Ngọc Duy]

Before the previous commit, get_pathname returns an array of PATH_MAX
length. Even if git_path() and similar functions does not use the
whole array, git_path() caller can, in theory.

After the commit, get_pathname() may return a buffer that has just
enough room for the returned string and git_path() caller should never
write beyond that.

Make git_path(), mkpath() and git_path_submodule() return a const
buffer to make sure callers do not write in it at all.

This could have been part of the previous commit, but the "const"
conversion is too much distraction from the core changes in path.c.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/checkout.c     | 2 +-
 builtin/clone.c        | 9 +++++----
 builtin/fetch.c        | 5 +++--
 builtin/fsck.c         | 4 ++--
 builtin/receive-pack.c | 2 +-
 builtin/remote.c       | 2 +-
 builtin/repack.c       | 8 +++++---
 cache.h                | 6 +++---
 fast-import.c          | 2 +-
 notes-merge.c          | 6 +++---
 path.c                 | 6 +++---
 refs.c                 | 8 ++++----
 run-command.c          | 4 ++--
 run-command.h          | 2 +-
 sha1_file.c            | 2 +-
 15 files changed, 36 insertions(+), 32 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index f1dc56e..6f74cfb 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -585,7 +585,7 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
 			if (opts->new_branch_log && !log_all_ref_updates) {
 				int temp;
 				char log_file[PATH_MAX];
-				char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
+				const char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 
 				temp = log_all_ref_updates;
 				log_all_ref_updates = 1;
diff --git a/builtin/clone.c b/builtin/clone.c
index b12989d..0878e73 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -289,16 +289,17 @@ static void copy_alternates(struct strbuf *src, struct strbuf *dst,
 	struct strbuf line = STRBUF_INIT;
 
 	while (strbuf_getline(&line, in, '\n') != EOF) {
-		char *abs_path, abs_buf[PATH_MAX];
+		char *abs_path;
 		if (!line.len || line.buf[0] == '#')
 			continue;
 		if (is_absolute_path(line.buf)) {
 			add_to_alternates_file(line.buf);
 			continue;
 		}
-		abs_path = mkpath("%s/objects/%s", src_repo, line.buf);
-		normalize_path_copy(abs_buf, abs_path);
-		add_to_alternates_file(abs_buf);
+		abs_path = mkpathdup("%s/objects/%s", src_repo, line.buf);
+		normalize_path_copy(abs_path, abs_path);
+		add_to_alternates_file(abs_path);
+		free(abs_path);
 	}
 	strbuf_release(&line);
 	fclose(in);
diff --git a/builtin/fetch.c b/builtin/fetch.c
index dd46b61..eb3180d 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -573,7 +573,8 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 	struct strbuf note = STRBUF_INIT;
 	const char *what, *kind;
 	struct ref *rm;
-	char *url, *filename = dry_run ? "/dev/null" : git_path("FETCH_HEAD");
+	char *url;
+	const char *filename = dry_run ? "/dev/null" : git_path("FETCH_HEAD");
 	int want_status;
 
 	fp = fopen(filename, "a");
@@ -807,7 +808,7 @@ static void check_not_current_branch(struct ref *ref_map)
 
 static int truncate_fetch_head(void)
 {
-	char *filename = git_path("FETCH_HEAD");
+	const char *filename = git_path("FETCH_HEAD");
 	FILE *fp = fopen(filename, "w");
 
 	if (!fp)
diff --git a/builtin/fsck.c b/builtin/fsck.c
index 8aadca1..d414962 100644
--- a/builtin/fsck.c
+++ b/builtin/fsck.c
@@ -225,12 +225,12 @@ static void check_unreachable_object(struct object *obj)
 			printf("dangling %s %s\n", typename(obj->type),
 			       sha1_to_hex(obj->sha1));
 		if (write_lost_and_found) {
-			char *filename = git_path("lost-found/%s/%s",
+			const char *filename = git_path("lost-found/%s/%s",
 				obj->type == OBJ_COMMIT ? "commit" : "other",
 				sha1_to_hex(obj->sha1));
 			FILE *f;
 
-			if (safe_create_leading_directories(filename)) {
+			if (safe_create_leading_directories_const(filename)) {
 				error("Could not create lost-found");
 				return;
 			}
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index c323081..3b64fef 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -599,7 +599,7 @@ static void run_update_post_hook(struct command *commands)
 	int argc;
 	const char **argv;
 	struct child_process proc;
-	char *hook;
+	const char *hook;
 
 	hook = find_hook("post-update");
 	for (argc = 0, cmd = commands; cmd; cmd = cmd->next) {
diff --git a/builtin/remote.c b/builtin/remote.c
index c9102e8..c9b67ff 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -582,7 +582,7 @@ static int migrate_file(struct remote *remote)
 {
 	struct strbuf buf = STRBUF_INIT;
 	int i;
-	char *path = NULL;
+	const char *path = NULL;
 
 	strbuf_addf(&buf, "remote.%s.url", remote->name);
 	for (i = 0; i < remote->url_nr; i++)
diff --git a/builtin/repack.c b/builtin/repack.c
index ff2216a..a64a4a9 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -285,7 +285,8 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	failed = 0;
 	for_each_string_list_item(item, &names) {
 		for (ext = 0; ext < ARRAY_SIZE(exts); ext++) {
-			char *fname, *fname_old;
+			const char *fname_old;
+			char *fname;
 			fname = mkpathdup("%s/pack-%s%s", packdir,
 						item->string, exts[ext].name);
 			if (!file_exists(fname)) {
@@ -313,7 +314,8 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	if (failed) {
 		struct string_list rollback_failure = STRING_LIST_INIT_DUP;
 		for_each_string_list_item(item, &rollback) {
-			char *fname, *fname_old;
+			const char *fname_old;
+			char *fname;
 			fname = mkpathdup("%s/%s", packdir, item->string);
 			fname_old = mkpath("%s/old-%s", packdir, item->string);
 			if (rename(fname_old, fname))
@@ -366,7 +368,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	/* Remove the "old-" files */
 	for_each_string_list_item(item, &names) {
 		for (ext = 0; ext < ARRAY_SIZE(exts); ext++) {
-			char *fname;
+			const char *fname;
 			fname = mkpath("%s/old-%s%s",
 					packdir,
 					item->string,
diff --git a/cache.h b/cache.h
index df65231..822017c 100644
--- a/cache.h
+++ b/cache.h
@@ -682,9 +682,9 @@ extern char *mkpathdup(const char *fmt, ...)
 	__attribute__((format (printf, 1, 2)));
 
 /* Return a statically allocated filename matching the sha1 signature */
-extern char *mkpath(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
-extern char *git_path(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
-extern char *git_path_submodule(const char *path, const char *fmt, ...)
+extern const char *mkpath(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
+extern const char *git_path(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
+extern const char *git_path_submodule(const char *path, const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
 
 /*
diff --git a/fast-import.c b/fast-import.c
index 6707a66..c74ea15 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -404,7 +404,7 @@ static void dump_marks_helper(FILE *, uintmax_t, struct mark_set *);
 
 static void write_crash_report(const char *err)
 {
-	char *loc = git_path("fast_import_crash_%"PRIuMAX, (uintmax_t) getpid());
+	const char *loc = git_path("fast_import_crash_%"PRIuMAX, (uintmax_t) getpid());
 	FILE *rpt = fopen(loc, "w");
 	struct branch *b;
 	unsigned long lu;
diff --git a/notes-merge.c b/notes-merge.c
index fd5fae2..a9e6b15 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -280,7 +280,7 @@ static void check_notes_merge_worktree(struct notes_merge_options *o)
 				    "(%s exists).", git_path("NOTES_MERGE_*"));
 		}
 
-		if (safe_create_leading_directories(git_path(
+		if (safe_create_leading_directories_const(git_path(
 				NOTES_MERGE_WORKTREE "/.test")))
 			die_errno("unable to create directory %s",
 				  git_path(NOTES_MERGE_WORKTREE));
@@ -295,8 +295,8 @@ static void write_buf_to_worktree(const unsigned char *obj,
 				  const char *buf, unsigned long size)
 {
 	int fd;
-	char *path = git_path(NOTES_MERGE_WORKTREE "/%s", sha1_to_hex(obj));
-	if (safe_create_leading_directories(path))
+	const char *path = git_path(NOTES_MERGE_WORKTREE "/%s", sha1_to_hex(obj));
+	if (safe_create_leading_directories_const(path))
 		die_errno("unable to create directory for '%s'", path);
 	if (file_exists(path))
 		die("found existing file at '%s'", path);
diff --git a/path.c b/path.c
index 42ef3af..a3f8826 100644
--- a/path.c
+++ b/path.c
@@ -106,7 +106,7 @@ char *mkpathdup(const char *fmt, ...)
 	return strbuf_detach(&sb, NULL);
 }
 
-char *mkpath(const char *fmt, ...)
+const char *mkpath(const char *fmt, ...)
 {
 	va_list args;
 	struct strbuf *pathname = get_pathname();
@@ -116,7 +116,7 @@ char *mkpath(const char *fmt, ...)
 	return cleanup_path(pathname->buf);
 }
 
-char *git_path(const char *fmt, ...)
+const char *git_path(const char *fmt, ...)
 {
 	struct strbuf *pathname = get_pathname();
 	va_list args;
@@ -152,7 +152,7 @@ void home_config_paths(char **global, char **xdg, char *file)
 	free(to_free);
 }
 
-char *git_path_submodule(const char *path, const char *fmt, ...)
+const char *git_path_submodule(const char *path, const char *fmt, ...)
 {
 	struct strbuf *buf = get_pathname();
 	const char *git_dir;
diff --git a/refs.c b/refs.c
index 20e2bf1..ce5968a 100644
--- a/refs.c
+++ b/refs.c
@@ -1441,7 +1441,7 @@ static int resolve_gitlink_ref_recursive(struct ref_cache *refs,
 {
 	int fd, len;
 	char buffer[128], *p;
-	char *path;
+	const char *path;
 
 	if (recursion > MAXDEPTH || strlen(refname) > MAXREFLEN)
 		return -1;
@@ -2254,7 +2254,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 					    const unsigned char *old_sha1,
 					    int flags, int *type_p)
 {
-	char *ref_file;
+	const char *ref_file;
 	const char *orig_refname = refname;
 	struct ref_lock *lock;
 	int last_errno = 0;
@@ -2317,7 +2317,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 		lock->force_write = 1;
 
  retry:
-	switch (safe_create_leading_directories(ref_file)) {
+	switch (safe_create_leading_directories_const(ref_file)) {
 	case SCLD_OK:
 		break; /* success */
 	case SCLD_VANISHED:
@@ -2755,7 +2755,7 @@ static int rename_tmp_log(const char *newrefname)
 	int attempts_remaining = 4;
 
  retry:
-	switch (safe_create_leading_directories(git_path("logs/%s", newrefname))) {
+	switch (safe_create_leading_directories_const(git_path("logs/%s", newrefname))) {
 	case SCLD_OK:
 		break; /* success */
 	case SCLD_VANISHED:
diff --git a/run-command.c b/run-command.c
index be07d4a..614b8ac 100644
--- a/run-command.c
+++ b/run-command.c
@@ -758,9 +758,9 @@ int finish_async(struct async *async)
 #endif
 }
 
-char *find_hook(const char *name)
+const char *find_hook(const char *name)
 {
-	char *path = git_path("hooks/%s", name);
+	const char *path = git_path("hooks/%s", name);
 	if (access(path, X_OK) < 0)
 		path = NULL;
 
diff --git a/run-command.h b/run-command.h
index ea73de3..890cc95 100644
--- a/run-command.h
+++ b/run-command.h
@@ -48,7 +48,7 @@ int start_command(struct child_process *);
 int finish_command(struct child_process *);
 int run_command(struct child_process *);
 
-extern char *find_hook(const char *name);
+extern const char *find_hook(const char *name);
 LAST_ARG_MUST_BE_NULL
 extern int run_hook_le(const char *const *env, const char *name, ...);
 extern int run_hook_ve(const char *const *env, const char *name, va_list args);
diff --git a/sha1_file.c b/sha1_file.c
index 34d527f..52768d6 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -401,7 +401,7 @@ void add_to_alternates_file(const char *reference)
 {
 	struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 	int fd = hold_lock_file_for_append(lock, git_path("objects/info/alternates"), LOCK_DIE_ON_ERROR);
-	char *alt = mkpath("%s\n", reference);
+	const char *alt = mkpath("%s\n", reference);
 	write_or_die(fd, alt, strlen(alt));
 	if (commit_lock_file(lock))
 		die("could not close alternates file");
-- 
1.9.1.346.ga2b5940

[PATCH v6 03/32] git_snpath(): retire and replace with strbuf_git_path()

[Nguyễn Thái Ngọc Duy]

In the previous patch, git_snpath() is modified to allocate a new
strbuf buffer because vsnpath() needs that. But that makes it
awkward because git_snpath() receives a pre-allocated buffer from
outside and has to copy data back. Rename it to strbuf_git_path()
and make it receive strbuf directly.

Using git_path() in update_refs_for_switch() which used to call
git_snpath() is safe because that function and all of its callers do
not keep any pointer to the round-robin buffer pool allocated by
get_pathname().

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/checkout.c | 13 +++++----
 cache.h            |  4 +--
 path.c             | 11 ++------
 refs.c             | 78 +++++++++++++++++++++++++++++++++---------------------
 refs.h             |  2 +-
 5 files changed, 61 insertions(+), 47 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 6f74cfb..7356799 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -584,18 +584,21 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
 		if (opts->new_orphan_branch) {
 			if (opts->new_branch_log && !log_all_ref_updates) {
 				int temp;
-				char log_file[PATH_MAX];
-				const char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
+				struct strbuf log_file = STRBUF_INIT;
+				int ret;
+				const char *ref_name;
 
+				ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 				temp = log_all_ref_updates;
 				log_all_ref_updates = 1;
-				if (log_ref_setup(ref_name, log_file, sizeof(log_file))) {
+				ret = log_ref_setup(ref_name, &log_file);
+				log_all_ref_updates = temp;
+				strbuf_release(&log_file);
+				if (ret) {
 					fprintf(stderr, _("Can not do reflog for '%s'\n"),
 					    opts->new_orphan_branch);
-					log_all_ref_updates = temp;
 					return;
 				}
-				log_all_ref_updates = temp;
 			}
 		}
 		else
diff --git a/cache.h b/cache.h
index 822017c..8faf947 100644
--- a/cache.h
+++ b/cache.h
@@ -674,8 +674,8 @@ extern int check_repository_format(void);
 
 extern char *mksnpath(char *buf, size_t n, const char *fmt, ...)
 	__attribute__((format (printf, 3, 4)));
-extern char *git_snpath(char *buf, size_t n, const char *fmt, ...)
-	__attribute__((format (printf, 3, 4)));
+extern void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
+	__attribute__((format (printf, 2, 3)));
 extern char *git_pathdup(const char *fmt, ...)
 	__attribute__((format (printf, 1, 2)));
 extern char *mkpathdup(const char *fmt, ...)
diff --git a/path.c b/path.c
index a3f8826..e545064 100644
--- a/path.c
+++ b/path.c
@@ -70,19 +70,12 @@ static void vsnpath(struct strbuf *buf, const char *fmt, va_list args)
 	strbuf_cleanup_path(buf);
 }
 
-char *git_snpath(char *buf, size_t n, const char *fmt, ...)
+void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 {
-	struct strbuf sb = STRBUF_INIT;
 	va_list args;
 	va_start(args, fmt);
-	vsnpath(&sb, fmt, args);
+	vsnpath(sb, fmt, args);
 	va_end(args);
-	if (sb.len >= n)
-		strlcpy(buf, bad_path, n);
-	else
-		memcpy(buf, sb.buf, sb.len + 1);
-	strbuf_release(&sb);
-	return buf;
 }
 
 char *git_pathdup(const char *fmt, ...)
diff --git a/refs.c b/refs.c
index ce5968a..45ab86d 100644
--- a/refs.c
+++ b/refs.c
@@ -1534,10 +1534,12 @@ static const char *handle_missing_loose_ref(const char *refname,
 
 const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int reading, int *flag)
 {
+	struct strbuf sb_path = STRBUF_INIT;
 	int depth = MAXDEPTH;
 	ssize_t len;
 	char buffer[256];
 	static char refname_buffer[256];
+	const char *ret;
 
 	if (flag)
 		*flag = 0;
@@ -1546,15 +1548,17 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 		return NULL;
 
 	for (;;) {
-		char path[PATH_MAX];
+		const char *path;
 		struct stat st;
 		char *buf;
 		int fd;
 
 		if (--depth < 0)
-			return NULL;
+			goto fail;
 
-		git_snpath(path, sizeof(path), "%s", refname);
+		strbuf_reset(&sb_path);
+		strbuf_git_path(&sb_path, "%s", refname);
+		path = sb_path.buf;
 
 		/*
 		 * We might have to loop back here to avoid a race
@@ -1568,10 +1572,11 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 	stat_ref:
 		if (lstat(path, &st) < 0) {
 			if (errno == ENOENT)
-				return handle_missing_loose_ref(refname, sha1,
-								reading, flag);
+				ret = handle_missing_loose_ref(refname, sha1,
+							       reading, flag);
 			else
-				return NULL;
+				ret = NULL;
+			goto done;
 		}
 
 		/* Follow "normalized" - ie "refs/.." symlinks by hand */
@@ -1582,7 +1587,7 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 					/* inconsistent with lstat; retry */
 					goto stat_ref;
 				else
-					return NULL;
+					goto fail;
 			}
 			buffer[len] = 0;
 			if (starts_with(buffer, "refs/") &&
@@ -1598,7 +1603,7 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 		/* Is it a directory? */
 		if (S_ISDIR(st.st_mode)) {
 			errno = EISDIR;
-			return NULL;
+			goto fail;
 		}
 
 		/*
@@ -1611,12 +1616,13 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 				/* inconsistent with lstat; retry */
 				goto stat_ref;
 			else
-				return NULL;
+				goto fail;
 		}
+
 		len = read_in_full(fd, buffer, sizeof(buffer)-1);
 		close(fd);
 		if (len < 0)
-			return NULL;
+			goto fail;
 		while (len && isspace(buffer[len-1]))
 			len--;
 		buffer[len] = '\0';
@@ -1633,9 +1639,10 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 			    (buffer[40] != '\0' && !isspace(buffer[40]))) {
 				if (flag)
 					*flag |= REF_ISBROKEN;
-				return NULL;
+				goto fail;
 			}
-			return refname;
+			ret = refname;
+			goto done;
 		}
 		if (flag)
 			*flag |= REF_ISSYMREF;
@@ -1645,10 +1652,15 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 		if (check_refname_format(buf, REFNAME_ALLOW_ONELEVEL)) {
 			if (flag)
 				*flag |= REF_ISBROKEN;
-			return NULL;
+			goto fail;
 		}
 		refname = strcpy(refname_buffer, buf);
 	}
+fail:
+	ret = NULL;
+done:
+	strbuf_release(&sb_path);
+	return ret;
 }
 
 char *resolve_refdup(const char *ref, unsigned char *sha1, int reading, int *flag)
@@ -2939,41 +2951,41 @@ static int copy_msg(char *buf, const char *msg)
 	return cp - buf;
 }
 
-int log_ref_setup(const char *refname, char *logfile, int bufsize)
+int log_ref_setup(const char *refname, struct strbuf *logfile)
 {
 	int logfd, oflags = O_APPEND | O_WRONLY;
 
-	git_snpath(logfile, bufsize, "logs/%s", refname);
+	strbuf_git_path(logfile, "logs/%s", refname);
 	if (log_all_ref_updates &&
 	    (starts_with(refname, "refs/heads/") ||
 	     starts_with(refname, "refs/remotes/") ||
 	     starts_with(refname, "refs/notes/") ||
 	     !strcmp(refname, "HEAD"))) {
-		if (safe_create_leading_directories(logfile) < 0)
+		if (safe_create_leading_directories(logfile->buf) < 0)
 			return error("unable to create directory for %s",
-				     logfile);
+				     logfile->buf);
 		oflags |= O_CREAT;
 	}
 
-	logfd = open(logfile, oflags, 0666);
+	logfd = open(logfile->buf, oflags, 0666);
 	if (logfd < 0) {
 		if (!(oflags & O_CREAT) && errno == ENOENT)
 			return 0;
 
 		if ((oflags & O_CREAT) && errno == EISDIR) {
-			if (remove_empty_directories(logfile)) {
+			if (remove_empty_directories(logfile->buf)) {
 				return error("There are still logs under '%s'",
-					     logfile);
+					     logfile->buf);
 			}
-			logfd = open(logfile, oflags, 0666);
+			logfd = open(logfile->buf, oflags, 0666);
 		}
 
 		if (logfd < 0)
 			return error("Unable to append to %s: %s",
-				     logfile, strerror(errno));
+				     logfile->buf, strerror(errno));
 	}
 
-	adjust_shared_perm(logfile);
+	adjust_shared_perm(logfile->buf);
 	close(logfd);
 	return 0;
 }
@@ -2984,20 +2996,22 @@ static int log_ref_write(const char *refname, const unsigned char *old_sha1,
 	int logfd, result, written, oflags = O_APPEND | O_WRONLY;
 	unsigned maxlen, len;
 	int msglen;
-	char log_file[PATH_MAX];
+	struct strbuf sb_log_file = STRBUF_INIT;
+	const char *log_file;
 	char *logrec;
 	const char *committer;
 
 	if (log_all_ref_updates < 0)
 		log_all_ref_updates = !is_bare_repository();
 
-	result = log_ref_setup(refname, log_file, sizeof(log_file));
+	result = log_ref_setup(refname, &sb_log_file);
 	if (result)
-		return result;
+		goto done;
+	log_file = sb_log_file.buf;
 
 	logfd = open(log_file, oflags);
 	if (logfd < 0)
-		return 0;
+		goto done;
 	msglen = msg ? strlen(msg) : 0;
 	committer = git_committer_info(0);
 	maxlen = strlen(committer) + msglen + 100;
@@ -3010,9 +3024,13 @@ static int log_ref_write(const char *refname, const unsigned char *old_sha1,
 		len += copy_msg(logrec + len - 1, msg) - 1;
 	written = len <= maxlen ? write_in_full(logfd, logrec, len) : -1;
 	free(logrec);
-	if (close(logfd) != 0 || written != len)
-		return error("Unable to append to %s", log_file);
-	return 0;
+	if (close(logfd) != 0 || written != len) {
+		error("Unable to append to %s", log_file);
+		result = -1;
+	}
+done:
+	strbuf_release(&sb_log_file);
+	return result;
 }
 
 static int is_branch(const char *refname)
diff --git a/refs.h b/refs.h
index 4e3050d..99d88a7 100644
--- a/refs.h
+++ b/refs.h
@@ -157,7 +157,7 @@ extern void unlock_ref(struct ref_lock *lock);
 extern int write_ref_sha1(struct ref_lock *lock, const unsigned char *sha1, const char *msg);
 
 /** Setup reflog before using. **/
-int log_ref_setup(const char *refname, char *logfile, int bufsize);
+int log_ref_setup(const char *refname, struct strbuf *logfile);
 
 /** Reads log for the value of ref during at_time. **/
 extern int read_ref_at(const char *refname, unsigned long at_time, int cnt,
-- 
1.9.1.346.ga2b5940

[PATCH v6 04/32] path.c: rename vsnpath() to do_git_path()

[Nguyễn Thái Ngọc Duy]

The name vsnpath() gives an impression that this is general path
handling function. It's not. This is the underlying implementation of
git_path(), git_pathdup() and strbuf_git_path() which will prefix
$GIT_DIR in the result string.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 path.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/path.c b/path.c
index e545064..2cb2e61 100644
--- a/path.c
+++ b/path.c
@@ -60,7 +60,7 @@ char *mksnpath(char *buf, size_t n, const char *fmt, ...)
 	return cleanup_path(buf);
 }
 
-static void vsnpath(struct strbuf *buf, const char *fmt, va_list args)
+static void do_git_path(struct strbuf *buf, const char *fmt, va_list args)
 {
 	const char *git_dir = get_git_dir();
 	strbuf_addstr(buf, git_dir);
@@ -74,7 +74,7 @@ void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 {
 	va_list args;
 	va_start(args, fmt);
-	vsnpath(sb, fmt, args);
+	do_git_path(sb, fmt, args);
 	va_end(args);
 }
 
@@ -83,7 +83,7 @@ char *git_pathdup(const char *fmt, ...)
 	struct strbuf path = STRBUF_INIT;
 	va_list args;
 	va_start(args, fmt);
-	vsnpath(&path, fmt, args);
+	do_git_path(&path, fmt, args);
 	va_end(args);
 	return strbuf_detach(&path, NULL);
 }
@@ -114,7 +114,7 @@ const char *git_path(const char *fmt, ...)
 	struct strbuf *pathname = get_pathname();
 	va_list args;
 	va_start(args, fmt);
-	vsnpath(pathname, fmt, args);
+	do_git_path(pathname, fmt, args);
 	va_end(args);
 	return pathname->buf;
 }
-- 
1.9.1.346.ga2b5940

[PATCH v6 05/32] path.c: group git_path(), git_pathdup() and strbuf_git_path() together

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 path.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/path.c b/path.c
index 2cb2e61..65881aa 100644
--- a/path.c
+++ b/path.c
@@ -78,6 +78,16 @@ void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 	va_end(args);
 }
 
+const char *git_path(const char *fmt, ...)
+{
+	struct strbuf *pathname = get_pathname();
+	va_list args;
+	va_start(args, fmt);
+	do_git_path(pathname, fmt, args);
+	va_end(args);
+	return pathname->buf;
+}
+
 char *git_pathdup(const char *fmt, ...)
 {
 	struct strbuf path = STRBUF_INIT;
@@ -109,16 +119,6 @@ const char *mkpath(const char *fmt, ...)
 	return cleanup_path(pathname->buf);
 }
 
-const char *git_path(const char *fmt, ...)
-{
-	struct strbuf *pathname = get_pathname();
-	va_list args;
-	va_start(args, fmt);
-	do_git_path(pathname, fmt, args);
-	va_end(args);
-	return pathname->buf;
-}
-
 void home_config_paths(char **global, char **xdg, char *file)
 {
 	char *xdg_home = getenv("XDG_CONFIG_HOME");
-- 
1.9.1.346.ga2b5940

[PATCH v6 06/32] setup_git_env: use git_pathdup instead of xmalloc + sprintf

[Nguyễn Thái Ngọc Duy]

From: Jeff King <peff@peff.net>

This is shorter, harder to get wrong, and more clearly
captures the intent.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 environment.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/environment.c b/environment.c
index 4dac5e9..4de7b81 100644
--- a/environment.c
+++ b/environment.c
@@ -135,15 +135,11 @@ static void setup_git_env(void)
 	gitfile = read_gitfile(git_dir);
 	git_dir = xstrdup(gitfile ? gitfile : git_dir);
 	git_object_dir = getenv(DB_ENVIRONMENT);
-	if (!git_object_dir) {
-		git_object_dir = xmalloc(strlen(git_dir) + 9);
-		sprintf(git_object_dir, "%s/objects", git_dir);
-	}
+	if (!git_object_dir)
+		git_object_dir = git_pathdup("objects");
 	git_index_file = getenv(INDEX_ENVIRONMENT);
-	if (!git_index_file) {
-		git_index_file = xmalloc(strlen(git_dir) + 7);
-		sprintf(git_index_file, "%s/index", git_dir);
-	}
+	if (!git_index_file)
+		git_index_file = git_pathdup("index");
 	git_graft_file = getenv(GRAFT_ENVIRONMENT);
 	if (!git_graft_file)
 		git_graft_file = git_pathdup("info/grafts");
-- 
1.9.1.346.ga2b5940

[PATCH v6 07/32] setup_git_env(): introduce git_path_from_env() helper

[Nguyễn Thái Ngọc Duy]

From: Jeff King <peff@peff.net>

"Check the value of an environment and fall back to a known path
inside $GIT_DIR" is repeated a few times to determine the location
of the data store, the index and the graft file, but the return
value of getenv is not guaranteed to survive across further
invocations of setenv or even getenv.

Make sure to xstrdup() the value we receive from getenv(3), and
encapsulate the pattern into a helper function.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 environment.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/environment.c b/environment.c
index 4de7b81..565f652 100644
--- a/environment.c
+++ b/environment.c
@@ -124,6 +124,12 @@ static char *expand_namespace(const char *raw_namespace)
 	return strbuf_detach(&buf, NULL);
 }
 
+static char *git_path_from_env(const char *envvar, const char *path)
+{
+	const char *value = getenv(envvar);
+	return value ? xstrdup(value) : git_pathdup("%s", path);
+}
+
 static void setup_git_env(void)
 {
 	const char *gitfile;
@@ -134,15 +140,9 @@ static void setup_git_env(void)
 		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
 	gitfile = read_gitfile(git_dir);
 	git_dir = xstrdup(gitfile ? gitfile : git_dir);
-	git_object_dir = getenv(DB_ENVIRONMENT);
-	if (!git_object_dir)
-		git_object_dir = git_pathdup("objects");
-	git_index_file = getenv(INDEX_ENVIRONMENT);
-	if (!git_index_file)
-		git_index_file = git_pathdup("index");
-	git_graft_file = getenv(GRAFT_ENVIRONMENT);
-	if (!git_graft_file)
-		git_graft_file = git_pathdup("info/grafts");
+	git_object_dir = git_path_from_env(DB_ENVIRONMENT, "objects");
+	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, "index");
+	git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, "info/grafts");
 	if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
 		check_replace_refs = 0;
 	namespace = expand_namespace(getenv(GIT_NAMESPACE_ENVIRONMENT));
-- 
1.9.1.346.ga2b5940

[PATCH v6 08/32] git_path(): be aware of file relocation in $GIT_DIR

[Nguyễn Thái Ngọc Duy]

We allow the user to relocate certain paths out of $GIT_DIR via
environment variables, e.g. GIT_OBJECT_DIRECTORY, GIT_INDEX_FILE and
GIT_GRAFT_FILE. Callers are not supposed to use git_path() or
git_pathdup() to get those paths. Instead they must use
get_object_directory(), get_index_file() and get_graft_file()
respectively. This is inconvenient and could be missed in review (for
example, there's git_path("objects/info/alternates") somewhere in
sha1_file.c).

This patch makes git_path() and git_pathdup() understand those
environment variables. So if you set GIT_OBJECT_DIRECTORY to /foo/bar,
git_path("objects/abc") should return /foo/bar/abc. The same is done
for the two remaining env variables.

"git rev-parse --git-path" is the wrapper for script use.

This patch kinda reverts a0279e1 (setup_git_env: use git_pathdup
instead of xmalloc + sprintf - 2014-06-19) because using git_pathdup
here would result in infinite recursion:

  setup_git_env() -> git_pathdup("objects") -> .. -> adjust_git_path()
  -> get_object_directory() -> oops, git_object_directory is NOT set
  yet -> setup_git_env()

I wanted to make git_pathdup_literal() that skips adjust_git_path().
But that won't work because later on when $GIT_COMMON_DIR is
introduced, git_pathdup_literal("objects") needs adjust_git_path() to
replace $GIT_DIR with $GIT_COMMON_DIR.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git-rev-parse.txt |  7 ++++++
 builtin/rev-parse.c             |  7 ++++++
 cache.h                         |  1 +
 environment.c                   | 19 +++++++++++-----
 path.c                          | 49 +++++++++++++++++++++++++++++++++++++++--
 t/t0060-path-utils.sh           | 19 ++++++++++++++++
 6 files changed, 95 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index 987395d..9465399 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -232,6 +232,13 @@ print a message to stderr and exit with nonzero status.
 	repository.  If <path> is a gitfile then the resolved path
 	to the real repository is printed.
 
+--git-path <path>::
+	Resolve "$GIT_DIR/<path>" and takes other path relocation
+	variables such as $GIT_OBJECT_DIRECTORY,
+	$GIT_INDEX_FILE... into account. For example, if
+	$GIT_OBJECT_DIRECTORY is set to /foo/bar then "git rev-parse
+	--git-path objects/abc" returns /foo/bar/abc.
+
 --show-cdup::
 	When the command is invoked from a subdirectory, show the
 	path of the top-level directory relative to the current
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 1a6122d..7606d43 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -529,6 +529,13 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
 
+		if (!strcmp(arg, "--git-path")) {
+			if (!argv[i + 1])
+				die("--git-path requires an argument");
+			puts(git_path("%s", argv[i + 1]));
+			i++;
+			continue;
+		}
 		if (as_is) {
 			if (show_file(arg, output_prefix) && as_is < 2)
 				verify_filename(prefix, arg, 0);
diff --git a/cache.h b/cache.h
index 8faf947..961f93d 100644
--- a/cache.h
+++ b/cache.h
@@ -612,6 +612,7 @@ extern int fsync_object_files;
 extern int core_preload_index;
 extern int core_apply_sparse_checkout;
 extern int precomposed_unicode;
+extern int git_db_env, git_index_env, git_graft_env;
 
 /*
  * The character that begins a commented line in user-editable file
diff --git a/environment.c b/environment.c
index 565f652..06bc8cc 100644
--- a/environment.c
+++ b/environment.c
@@ -83,6 +83,7 @@ static size_t namespace_len;
 
 static const char *git_dir;
 static char *git_object_dir, *git_index_file, *git_graft_file;
+int git_db_env, git_index_env, git_graft_env;
 
 /*
  * Repository-local GIT_* environment variables; see cache.h for details.
@@ -124,10 +125,18 @@ static char *expand_namespace(const char *raw_namespace)
 	return strbuf_detach(&buf, NULL);
 }
 
-static char *git_path_from_env(const char *envvar, const char *path)
+static char *git_path_from_env(const char *envvar, const char *path,
+			       int* fromenv)
 {
 	const char *value = getenv(envvar);
-	return value ? xstrdup(value) : git_pathdup("%s", path);
+	if (!value) {
+		char *buf = xmalloc(strlen(git_dir) + strlen(path) + 2);
+		sprintf(buf, "%s/%s", git_dir, path);
+		return buf;
+	}
+	if (fromenv)
+		*fromenv = 1;
+	return xstrdup(value);
 }
 
 static void setup_git_env(void)
@@ -140,9 +149,9 @@ static void setup_git_env(void)
 		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
 	gitfile = read_gitfile(git_dir);
 	git_dir = xstrdup(gitfile ? gitfile : git_dir);
-	git_object_dir = git_path_from_env(DB_ENVIRONMENT, "objects");
-	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, "index");
-	git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, "info/grafts");
+	git_object_dir = git_path_from_env(DB_ENVIRONMENT, "objects", &git_db_env);
+	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, "index", &git_index_env);
+	git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, "info/grafts", &git_graft_env);
 	if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
 		check_replace_refs = 0;
 	namespace = expand_namespace(getenv(GIT_NAMESPACE_ENVIRONMENT));
diff --git a/path.c b/path.c
index 65881aa..3deb80c 100644
--- a/path.c
+++ b/path.c
@@ -60,13 +60,58 @@ char *mksnpath(char *buf, size_t n, const char *fmt, ...)
 	return cleanup_path(buf);
 }
 
+static int dir_prefix(const char *buf, const char *dir)
+{
+	int len = strlen(dir);
+	return !strncmp(buf, dir, len) &&
+		(is_dir_sep(buf[len]) || buf[len] == '\0');
+}
+
+/* $buf =~ m|$dir/+$file| but without regex */
+static int is_dir_file(const char *buf, const char *dir, const char *file)
+{
+	int len = strlen(dir);
+	if (strncmp(buf, dir, len) || !is_dir_sep(buf[len]))
+		return 0;
+	while (is_dir_sep(buf[len]))
+		len++;
+	return !strcmp(buf + len, file);
+}
+
+static void replace_dir(struct strbuf *buf, int len, const char *newdir)
+{
+	int newlen = strlen(newdir);
+	int need_sep = (buf->buf[len] && !is_dir_sep(buf->buf[len])) &&
+		!is_dir_sep(newdir[newlen - 1]);
+	if (need_sep)
+		len--;	 /* keep one char, to be replaced with '/'  */
+	strbuf_splice(buf, 0, len, newdir, newlen);
+	if (need_sep)
+		buf->buf[newlen] = '/';
+}
+
+static void adjust_git_path(struct strbuf *buf, int git_dir_len)
+{
+	const char *base = buf->buf + git_dir_len;
+	if (git_graft_env && is_dir_file(base, "info", "grafts"))
+		strbuf_splice(buf, 0, buf->len,
+			      get_graft_file(), strlen(get_graft_file()));
+	else if (git_index_env && !strcmp(base, "index"))
+		strbuf_splice(buf, 0, buf->len,
+			      get_index_file(), strlen(get_index_file()));
+	else if (git_db_env && dir_prefix(base, "objects"))
+		replace_dir(buf, git_dir_len + 7, get_object_directory());
+}
+
 static void do_git_path(struct strbuf *buf, const char *fmt, va_list args)
 {
-	const char *git_dir = get_git_dir();
-	strbuf_addstr(buf, git_dir);
+	int gitdir_len;
+	strbuf_addstr(buf, get_git_dir());
 	if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 		strbuf_addch(buf, '/');
+	gitdir_len = buf->len;
 	strbuf_vaddf(buf, fmt, args);
+	adjust_git_path(buf, gitdir_len);
 	strbuf_cleanup_path(buf);
 }
 
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index c0143a0..33d2818 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -19,6 +19,14 @@ relative_path() {
 	"test \"\$(test-path-utils relative_path '$1' '$2')\" = '$expected'"
 }
 
+test_git_path() {
+	test_expect_success "git-path $1 $2 => $3" "
+		$1 git rev-parse --git-path $2 >actual &&
+		echo $3 >expect &&
+		test_cmp expect actual
+	"
+}
+
 # On Windows, we are using MSYS's bash, which mangles the paths.
 # Absolute paths are anchored at the MSYS installation directory,
 # which means that the path / accounts for this many characters:
@@ -244,4 +252,15 @@ relative_path "<null>"		"<empty>"	./
 relative_path "<null>"		"<null>"	./
 relative_path "<null>"		/foo/a/b	./
 
+test_git_path A=B                info/grafts .git/info/grafts
+test_git_path GIT_GRAFT_FILE=foo info/grafts foo
+test_git_path GIT_GRAFT_FILE=foo info/////grafts foo
+test_git_path GIT_INDEX_FILE=foo index foo
+test_git_path GIT_INDEX_FILE=foo index/foo .git/index/foo
+test_git_path GIT_INDEX_FILE=foo index2 .git/index2
+test_expect_success 'setup fake objects directory foo' 'mkdir foo'
+test_git_path GIT_OBJECT_DIRECTORY=foo objects foo
+test_git_path GIT_OBJECT_DIRECTORY=foo objects/foo foo/foo
+test_git_path GIT_OBJECT_DIRECTORY=foo objects2 .git/objects2
+
 test_done
-- 
1.9.1.346.ga2b5940

[PATCH v6 09/32] *.sh: respect $GIT_INDEX_FILE

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 git-pull.sh  | 2 +-
 git-stash.sh | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/git-pull.sh b/git-pull.sh
index 18a394f..6ab0c31 100755
--- a/git-pull.sh
+++ b/git-pull.sh
@@ -240,7 +240,7 @@ test true = "$rebase" && {
 	if ! git rev-parse -q --verify HEAD >/dev/null
 	then
 		# On an unborn branch
-		if test -f "$GIT_DIR/index"
+		if test -f "$(git rev-parse --git-path index)"
 		then
 			die "$(gettext "updating an unborn branch with changes added to the index")"
 		fi
diff --git a/git-stash.sh b/git-stash.sh
index bcc757b..393e1ec 100755
--- a/git-stash.sh
+++ b/git-stash.sh
@@ -20,7 +20,7 @@ require_work_tree
 cd_to_toplevel
 
 TMP="$GIT_DIR/.git-stash.$$"
-TMPindex=${GIT_INDEX_FILE-"$GIT_DIR/index"}.stash.$$
+TMPindex=${GIT_INDEX_FILE-"$(git rev-parse --git-path index)"}.stash.$$
 trap 'rm -f "$TMP-"* "$TMPindex"' 0
 
 ref_stash=refs/stash
-- 
1.9.1.346.ga2b5940

[PATCH v6 10/32] reflog: avoid constructing .lock path with git_path

[Nguyễn Thái Ngọc Duy]

Among pathnames in $GIT_DIR, e.g. "index" or "packed-refs", we want to
automatically and silently map some of them to the $GIT_DIR of the
repository we are borrowing from via $GIT_COMMON_DIR mechanism.  When
we formulate the pathname for its lockfile, we want it to be in the
same location as its final destination.  "index" is not shared and
needs to remain in the borrowing repository, while "packed-refs" is
shared and needs to go to the borrowed repository.

git_path() could be taught about the ".lock" suffix and map
"index.lock" and "packed-refs.lock" the same way their basenames are
mapped, but instead the caller can help by asking where the basename
(e.g. "index") is mapped to git_path() and then appending ".lock"
after the mapping is done.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/reflog.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/reflog.c b/builtin/reflog.c
index e8a8fb1..9bd874d 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c
@@ -372,7 +372,7 @@ static int expire_reflog(const char *ref, const unsigned char *sha1, int unused,
 	if (!reflog_exists(ref))
 		goto finish;
 	if (!cmd->dry_run) {
-		newlog_path = git_pathdup("logs/%s.lock", ref);
+		newlog_path = mkpathdup("%s.lock", log_file);
 		cb.newlog = fopen(newlog_path, "w");
 	}
 
-- 
1.9.1.346.ga2b5940

[PATCH v6 11/32] fast-import: use git_path() for accessing .git dir instead of get_git_dir()

[Nguyễn Thái Ngọc Duy]

This allows git_path() to redirect info/fast-import to another place
if needed

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 fast-import.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/fast-import.c b/fast-import.c
index c74ea15..e8ec34d 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -3123,12 +3123,9 @@ static void parse_progress(void)
 
 static char* make_fast_import_path(const char *path)
 {
-	struct strbuf abs_path = STRBUF_INIT;
-
 	if (!relative_marks_paths || is_absolute_path(path))
 		return xstrdup(path);
-	strbuf_addf(&abs_path, "%s/info/fast-import/%s", get_git_dir(), path);
-	return strbuf_detach(&abs_path, NULL);
+	return xstrdup(git_path("info/fast-import/%s", path));
 }
 
 static void option_import_marks(const char *marks,
-- 
1.9.1.346.ga2b5940

[PATCH v6 12/32] commit: use SEQ_DIR instead of hardcoding "sequencer"

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/commit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index 84cec9a..9f2aba3 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -156,7 +156,7 @@ static void determine_whence(struct wt_status *s)
 		whence = FROM_MERGE;
 	else if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
 		whence = FROM_CHERRY_PICK;
-		if (file_exists(git_path("sequencer")))
+		if (file_exists(git_path(SEQ_DIR)))
 			sequencer_in_use = 1;
 	}
 	else
-- 
1.9.1.346.ga2b5940

[PATCH v6 13/32] $GIT_COMMON_DIR: a new environment variable

[Nguyễn Thái Ngọc Duy]

This variable is intended to support multiple working directories
attached to a repository. Such a repository may have a main working
directory, created by either "git init" or "git clone" and one or more
linked working directories. These working directories and the main
repository share the same repository directory.

In linked working directories, $GIT_COMMON_DIR must be defined to point
to the real repository directory and $GIT_DIR points to an unused
subdirectory inside $GIT_COMMON_DIR. File locations inside the
repository are reorganized from the linked worktree view point:

 - worktree-specific such as HEAD, logs/HEAD, index, other top-level
   refs and unrecognized files are from $GIT_DIR.

 - the rest like objects, refs, info, hooks, packed-refs, shallow...
   are from $GIT_COMMON_DIR (except info/sparse-checkout, but that's
   a separate patch)

Scripts are supposed to retrieve paths in $GIT_DIR with "git rev-parse
--git-path", which will take care of "$GIT_DIR vs $GIT_COMMON_DIR"
business.

The redirection is done by git_path(), git_pathdup() and
strbuf_git_path(). The selected list of paths goes to $GIT_COMMON_DIR,
not the other way around in case a developer adds a new
worktree-specific file and it's accidentally promoted to be shared
across repositories (this includes unknown files added by third party
commands)

The list of known files that belong to $GIT_DIR are:

ADD_EDIT.patch BISECT_ANCESTORS_OK BISECT_EXPECTED_REV BISECT_LOG
BISECT_NAMES CHERRY_PICK_HEAD COMMIT_MSG FETCH_HEAD HEAD MERGE_HEAD
MERGE_MODE MERGE_RR NOTES_EDITMSG NOTES_MERGE_WORKTREE ORIG_HEAD
REVERT_HEAD SQUASH_MSG TAG_EDITMSG fast_import_crash_* logs/HEAD
next-index-* rebase-apply rebase-merge rsync-refs-* sequencer/*
shallow_*

Path mapping is NOT done for git_path_submodule(). Multi-checkouts are
not supported as submodules.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git.txt                  |  8 +++++++
 Documentation/gitrepository-layout.txt | 42 ++++++++++++++++++++++++++--------
 cache.h                                |  4 +++-
 environment.c                          | 28 +++++++++++++++++------
 path.c                                 | 34 +++++++++++++++++++++++++++
 t/t0060-path-utils.sh                  | 15 ++++++++++++
 6 files changed, 114 insertions(+), 17 deletions(-)

diff --git a/Documentation/git.txt b/Documentation/git.txt
index 7924209..749052f 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -788,6 +788,14 @@ Git so take care if using Cogito etc.
 	an explicit repository directory set via 'GIT_DIR' or on the
 	command line.
 
+'GIT_COMMON_DIR'::
+	If this variable is set to a path, non-worktree files that are
+	normally in $GIT_DIR will be taken from this path
+	instead. Worktree-specific files such as HEAD or index are
+	taken from $GIT_DIR. See linkgit:gitrepository-layout[5] for
+	details. This variable has lower precedence than other path
+	variables such as GIT_INDEX_FILE, GIT_OBJECT_DIRECTORY...
+
 Git Commits
 ~~~~~~~~~~~
 'GIT_AUTHOR_NAME'::
diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
index 17d2ea6..7629e38 100644
--- a/Documentation/gitrepository-layout.txt
+++ b/Documentation/gitrepository-layout.txt
@@ -46,6 +46,9 @@ of incomplete object store is not suitable to be published for
 use with dumb transports but otherwise is OK as long as
 `objects/info/alternates` points at the object stores it
 borrows from.
++
+This directory is ignored if $GIT_COMMON_DIR is set and
+"$GIT_COMMON_DIR/objects" will be used instead.
 
 objects/[0-9a-f][0-9a-f]::
 	A newly created object is stored in its own file.
@@ -92,7 +95,8 @@ refs::
 	References are stored in subdirectories of this
 	directory.  The 'git prune' command knows to preserve
 	objects reachable from refs found in this directory and
-	its subdirectories.
+	its subdirectories. This directory is ignored if $GIT_COMMON_DIR
+	is set and "$GIT_COMMON_DIR/refs" will be used instead.
 
 refs/heads/`name`::
 	records tip-of-the-tree commit objects of branch `name`
@@ -114,7 +118,8 @@ refs/replace/`<obj-sha1>`::
 packed-refs::
 	records the same information as refs/heads/, refs/tags/,
 	and friends record in a more efficient way.  See
-	linkgit:git-pack-refs[1].
+	linkgit:git-pack-refs[1]. This file is ignored if $GIT_COMMON_DIR
+	is set and "$GIT_COMMON_DIR/packed-refs" will be used instead.
 
 HEAD::
 	A symref (see glossary) to the `refs/heads/` namespace
@@ -133,6 +138,11 @@ being a symref to point at the current branch.  Such a state
 is often called 'detached HEAD.'  See linkgit:git-checkout[1]
 for details.
 
+config::
+	Repository specific configuration file. This file is ignored
+	$GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/config" will be
+	used instead.
+
 branches::
 	A slightly deprecated way to store shorthands to be used
 	to specify a URL to 'git fetch', 'git pull' and 'git push'.
@@ -140,7 +150,10 @@ branches::
 	'name' can be given to these commands in place of
 	'repository' argument.  See the REMOTES section in
 	linkgit:git-fetch[1] for details.  This mechanism is legacy
-	and not likely to be found in modern repositories.
+	and not likely to be found in modern repositories. This
+	directory is ignored if $GIT_COMMON_DIR is set and
+	"$GIT_COMMON_DIR/branches" will be used instead.
+
 
 hooks::
 	Hooks are customization scripts used by various Git
@@ -149,7 +162,9 @@ hooks::
 	default.  To enable, the `.sample` suffix has to be
 	removed from the filename by renaming.
 	Read linkgit:githooks[5] for more details about
-	each hook.
+	each hook. This directory is ignored if $GIT_COMMON_DIR is set
+	and "$GIT_COMMON_DIR/hooks" will be used instead.
+
 
 index::
 	The current index file for the repository.  It is
@@ -157,7 +172,8 @@ index::
 
 info::
 	Additional information about the repository is recorded
-	in this directory.
+	in this directory. This directory is ignored if $GIT_COMMON_DIR
+	is set and "$GIT_COMMON_DIR/index" will be used instead.
 
 info/refs::
 	This file helps dumb transports discover what refs are
@@ -197,12 +213,16 @@ remotes::
 	when interacting with remote repositories via 'git fetch',
 	'git pull' and 'git push' commands.  See the REMOTES section
 	in linkgit:git-fetch[1] for details.  This mechanism is legacy
-	and not likely to be found in modern repositories.
+	and not likely to be found in modern repositories. This
+	directory is ignored if $GIT_COMMON_DIR is set and
+	"$GIT_COMMON_DIR/remotes" will be used instead.
 
 logs::
 	Records of changes made to refs are stored in this
 	directory.  See linkgit:git-update-ref[1]
-	for more information.
+	for more information. This directory is ignored
+	$GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/logs" will be used
+	instead.
 
 logs/refs/heads/`name`::
 	Records all changes made to the branch tip named `name`.
@@ -213,10 +233,14 @@ logs/refs/tags/`name`::
 shallow::
 	This is similar to `info/grafts` but is internally used
 	and maintained by shallow clone mechanism.  See `--depth`
-	option to linkgit:git-clone[1] and linkgit:git-fetch[1].
+	option to linkgit:git-clone[1] and linkgit:git-fetch[1]. This
+	file is ignored if $GIT_COMMON_DIR is set and
+	"$GIT_COMMON_DIR/shallow" will be used instead.
 
 modules::
-	Contains the git-repositories of the submodules.
+	Contains the git-repositories of the submodules. This
+	directory is ignored if $GIT_COMMON_DIR is set and
+	"$GIT_COMMON_DIR/modules" will be used instead.
 
 SEE ALSO
 --------
diff --git a/cache.h b/cache.h
index 961f93d..8052ddc 100644
--- a/cache.h
+++ b/cache.h
@@ -362,6 +362,7 @@ static inline enum object_type object_type(unsigned int mode)
 
 /* Double-check local_repo_env below if you add to this list. */
 #define GIT_DIR_ENVIRONMENT "GIT_DIR"
+#define GIT_COMMON_DIR_ENVIRONMENT "GIT_COMMON_DIR"
 #define GIT_NAMESPACE_ENVIRONMENT "GIT_NAMESPACE"
 #define GIT_WORK_TREE_ENVIRONMENT "GIT_WORK_TREE"
 #define GIT_PREFIX_ENVIRONMENT "GIT_PREFIX"
@@ -415,6 +416,7 @@ extern int is_inside_git_dir(void);
 extern char *git_work_tree_cfg;
 extern int is_inside_work_tree(void);
 extern const char *get_git_dir(void);
+extern const char *get_git_common_dir(void);
 extern int is_git_directory(const char *path);
 extern char *get_object_directory(void);
 extern char *get_index_file(void);
@@ -612,7 +614,7 @@ extern int fsync_object_files;
 extern int core_preload_index;
 extern int core_apply_sparse_checkout;
 extern int precomposed_unicode;
-extern int git_db_env, git_index_env, git_graft_env;
+extern int git_db_env, git_index_env, git_graft_env, git_common_dir_env;
 
 /*
  * The character that begins a commented line in user-editable file
diff --git a/environment.c b/environment.c
index 06bc8cc..76eb38c 100644
--- a/environment.c
+++ b/environment.c
@@ -81,9 +81,9 @@ static char *work_tree;
 static const char *namespace;
 static size_t namespace_len;
 
-static const char *git_dir;
+static const char *git_dir, *git_common_dir;
 static char *git_object_dir, *git_index_file, *git_graft_file;
-int git_db_env, git_index_env, git_graft_env;
+int git_db_env, git_index_env, git_graft_env, git_common_dir_env;
 
 /*
  * Repository-local GIT_* environment variables; see cache.h for details.
@@ -125,8 +125,8 @@ static char *expand_namespace(const char *raw_namespace)
 	return strbuf_detach(&buf, NULL);
 }
 
-static char *git_path_from_env(const char *envvar, const char *path,
-			       int* fromenv)
+static char *git_path_from_env(const char *envvar, const char *git_dir,
+			       const char *path, int* fromenv)
 {
 	const char *value = getenv(envvar);
 	if (!value) {
@@ -149,9 +149,18 @@ static void setup_git_env(void)
 		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
 	gitfile = read_gitfile(git_dir);
 	git_dir = xstrdup(gitfile ? gitfile : git_dir);
-	git_object_dir = git_path_from_env(DB_ENVIRONMENT, "objects", &git_db_env);
-	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, "index", &git_index_env);
-	git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, "info/grafts", &git_graft_env);
+	git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
+	if (git_common_dir) {
+		git_common_dir_env = 1;
+		git_common_dir = xstrdup(git_common_dir);
+	} else
+		git_common_dir = git_dir;
+	git_object_dir = git_path_from_env(DB_ENVIRONMENT, git_common_dir,
+					   "objects", &git_db_env);
+	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, git_dir,
+					   "index", &git_index_env);
+	git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, git_dir,
+					   "info/grafts", &git_graft_env);
 	if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
 		check_replace_refs = 0;
 	namespace = expand_namespace(getenv(GIT_NAMESPACE_ENVIRONMENT));
@@ -174,6 +183,11 @@ const char *get_git_dir(void)
 	return git_dir;
 }
 
+const char *get_git_common_dir(void)
+{
+	return git_common_dir;
+}
+
 const char *get_git_namespace(void)
 {
 	if (!namespace)
diff --git a/path.c b/path.c
index 3deb80c..8a6586c 100644
--- a/path.c
+++ b/path.c
@@ -90,6 +90,38 @@ static void replace_dir(struct strbuf *buf, int len, const char *newdir)
 		buf->buf[newlen] = '/';
 }
 
+static const char *common_list[] = {
+	"/branches", "/hooks", "/info", "/logs", "/lost-found", "/modules",
+	"/objects", "/refs", "/remotes", "/rr-cache", "/svn",
+	"config", "gc.pid", "packed-refs", "shallow",
+	NULL
+};
+
+static void update_common_dir(struct strbuf *buf, int git_dir_len)
+{
+	char *base = buf->buf + git_dir_len;
+	const char **p;
+
+	if (is_dir_file(base, "logs", "HEAD"))
+		return;	/* keep this in $GIT_DIR */
+	for (p = common_list; *p; p++) {
+		const char *path = *p;
+		int is_dir = 0;
+		if (*path == '/') {
+			path++;
+			is_dir = 1;
+		}
+		if (is_dir && dir_prefix(base, path)) {
+			replace_dir(buf, git_dir_len, get_git_common_dir());
+			return;
+		}
+		if (!is_dir && !strcmp(base, path)) {
+			replace_dir(buf, git_dir_len, get_git_common_dir());
+			return;
+		}
+	}
+}
+
 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 {
 	const char *base = buf->buf + git_dir_len;
@@ -101,6 +133,8 @@ static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 			      get_index_file(), strlen(get_index_file()));
 	else if (git_db_env && dir_prefix(base, "objects"))
 		replace_dir(buf, git_dir_len + 7, get_object_directory());
+	else if (git_common_dir_env)
+		update_common_dir(buf, git_dir_len);
 }
 
 static void do_git_path(struct strbuf *buf, const char *fmt, va_list args)
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 33d2818..2dabcef 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -262,5 +262,20 @@ test_expect_success 'setup fake objects directory foo' 'mkdir foo'
 test_git_path GIT_OBJECT_DIRECTORY=foo objects foo
 test_git_path GIT_OBJECT_DIRECTORY=foo objects/foo foo/foo
 test_git_path GIT_OBJECT_DIRECTORY=foo objects2 .git/objects2
+test_expect_success 'setup common repository' 'git --git-dir=bar init'
+test_git_path GIT_COMMON_DIR=bar index                    .git/index
+test_git_path GIT_COMMON_DIR=bar HEAD                     .git/HEAD
+test_git_path GIT_COMMON_DIR=bar logs/HEAD                .git/logs/HEAD
+test_git_path GIT_COMMON_DIR=bar objects                  bar/objects
+test_git_path GIT_COMMON_DIR=bar objects/bar              bar/objects/bar
+test_git_path GIT_COMMON_DIR=bar info/exclude             bar/info/exclude
+test_git_path GIT_COMMON_DIR=bar remotes/bar              bar/remotes/bar
+test_git_path GIT_COMMON_DIR=bar branches/bar             bar/branches/bar
+test_git_path GIT_COMMON_DIR=bar logs/refs/heads/master   bar/logs/refs/heads/master
+test_git_path GIT_COMMON_DIR=bar refs/heads/master        bar/refs/heads/master
+test_git_path GIT_COMMON_DIR=bar hooks/me                 bar/hooks/me
+test_git_path GIT_COMMON_DIR=bar config                   bar/config
+test_git_path GIT_COMMON_DIR=bar packed-refs              bar/packed-refs
+test_git_path GIT_COMMON_DIR=bar shallow                  bar/shallow
 
 test_done
-- 
1.9.1.346.ga2b5940

[PATCH v6 14/32] git-sh-setup.sh: use rev-parse --git-path to get $GIT_DIR/objects

[Nguyễn Thái Ngọc Duy]

If $GIT_COMMON_DIR is set, $GIT_OBJECT_DIRECTORY should be
$GIT_COMMON_DIR/objects, not $GIT_DIR/objects. Just let rev-parse
--git-path handle it.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 git-sh-setup.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/git-sh-setup.sh b/git-sh-setup.sh
index 9447980..d3dbb2f 100644
--- a/git-sh-setup.sh
+++ b/git-sh-setup.sh
@@ -345,7 +345,7 @@ then
 		echo >&2 "Unable to determine absolute path of git directory"
 		exit 1
 	}
-	: ${GIT_OBJECT_DIRECTORY="$GIT_DIR/objects"}
+	: ${GIT_OBJECT_DIRECTORY="$(git rev-parse --git-path objects)"}
 fi
 
 peel_committish () {
-- 
1.9.1.346.ga2b5940

[PATCH v6 15/32] *.sh: avoid hardcoding $GIT_DIR/hooks/...

[Nguyễn Thái Ngọc Duy]

If $GIT_COMMON_DIR is set, it should be $GIT_COMMON_DIR/hooks/, not
$GIT_DIR/hooks/. Just let rev-parse --git-path handle it.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 git-am.sh                              | 22 +++++++++++-----------
 git-rebase--interactive.sh             |  6 +++---
 git-rebase--merge.sh                   |  6 ++----
 git-rebase.sh                          |  4 ++--
 templates/hooks--applypatch-msg.sample |  4 ++--
 templates/hooks--pre-applypatch.sample |  4 ++--
 6 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/git-am.sh b/git-am.sh
index ee61a77..66803d1 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -810,10 +810,10 @@ To restore the original branch and stop patching run \"\$cmdline --abort\"."
 		continue
 	fi
 
-	if test -x "$GIT_DIR"/hooks/applypatch-msg
+	hook="$(git rev-parse --git-path hooks/applypatch-msg)"
+	if test -x "$hook"
 	then
-		"$GIT_DIR"/hooks/applypatch-msg "$dotest/final-commit" ||
-		stop_here $this
+		"$hook" "$dotest/final-commit" || stop_here $this
 	fi
 
 	if test -f "$dotest/final-commit"
@@ -887,9 +887,10 @@ did you forget to use 'git add'?"
 		stop_here_user_resolve $this
 	fi
 
-	if test -x "$GIT_DIR"/hooks/pre-applypatch
+	hook="$(git rev-parse --git-path hooks/pre-applypatch)"
+	if test -x "$hook"
 	then
-		"$GIT_DIR"/hooks/pre-applypatch || stop_here $this
+		"$hook" || stop_here $this
 	fi
 
 	tree=$(git write-tree) &&
@@ -916,18 +917,17 @@ did you forget to use 'git add'?"
 		echo "$(cat "$dotest/original-commit") $commit" >> "$dotest/rewritten"
 	fi
 
-	if test -x "$GIT_DIR"/hooks/post-applypatch
-	then
-		"$GIT_DIR"/hooks/post-applypatch
-	fi
+	hook="$(git rev-parse --git-path hooks/post-applypatch)"
+	test -x "$hook" && "$hook"
 
 	go_next
 done
 
 if test -s "$dotest"/rewritten; then
     git notes copy --for-rewrite=rebase < "$dotest"/rewritten
-    if test -x "$GIT_DIR"/hooks/post-rewrite; then
-	"$GIT_DIR"/hooks/post-rewrite rebase < "$dotest"/rewritten
+    hook="$(git rev-parse --git-path hooks/post-rewrite)"
+    if test -x "$hook"; then
+	"$hook" rebase < "$dotest"/rewritten
     fi
 fi
 
diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index 7e1eda0..e8995f9 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -642,9 +642,9 @@ do_next () {
 		git notes copy --for-rewrite=rebase < "$rewritten_list" ||
 		true # we don't care if this copying failed
 	} &&
-	if test -x "$GIT_DIR"/hooks/post-rewrite &&
-		test -s "$rewritten_list"; then
-		"$GIT_DIR"/hooks/post-rewrite rebase < "$rewritten_list"
+	hook="$(git rev-parse --git-path hooks/post-rewrite)"
+	if test -x "$hook" && test -s "$rewritten_list"; then
+		"$hook" rebase < "$rewritten_list"
 		true # we don't care if this hook failed
 	fi &&
 	warn "Successfully rebased and updated $head_name."
diff --git a/git-rebase--merge.sh b/git-rebase--merge.sh
index d3fb67d..2cc2a6d 100644
--- a/git-rebase--merge.sh
+++ b/git-rebase--merge.sh
@@ -94,10 +94,8 @@ finish_rb_merge () {
 	if test -s "$state_dir"/rewritten
 	then
 		git notes copy --for-rewrite=rebase <"$state_dir"/rewritten
-		if test -x "$GIT_DIR"/hooks/post-rewrite
-		then
-			"$GIT_DIR"/hooks/post-rewrite rebase <"$state_dir"/rewritten
-		fi
+		hook="$(git rev-parse --git-path hooks/post-rewrite)"
+		test -x "$hook" && "$hook" rebase <"$state_dir"/rewritten
 	fi
 	say All done.
 }
diff --git a/git-rebase.sh b/git-rebase.sh
index 06c810b..d60e710 100755
--- a/git-rebase.sh
+++ b/git-rebase.sh
@@ -201,9 +201,9 @@ run_specific_rebase () {
 
 run_pre_rebase_hook () {
 	if test -z "$ok_to_skip_pre_rebase" &&
-	   test -x "$GIT_DIR/hooks/pre-rebase"
+	   test -x "$(git rev-parse --git-path hooks/pre-rebase)"
 	then
-		"$GIT_DIR/hooks/pre-rebase" ${1+"$@"} ||
+		"$(git rev-parse --git-path hooks/pre-rebase)" ${1+"$@"} ||
 		die "$(gettext "The pre-rebase hook refused to rebase.")"
 	fi
 }
diff --git a/templates/hooks--applypatch-msg.sample b/templates/hooks--applypatch-msg.sample
index 8b2a2fe..a5d7b84 100755
--- a/templates/hooks--applypatch-msg.sample
+++ b/templates/hooks--applypatch-msg.sample
@@ -10,6 +10,6 @@
 # To enable this hook, rename this file to "applypatch-msg".
 
 . git-sh-setup
-test -x "$GIT_DIR/hooks/commit-msg" &&
-	exec "$GIT_DIR/hooks/commit-msg" ${1+"$@"}
+commitmsg="$(git rev-parse --git-path hooks/commit-msg)"
+test -x "$commitmsg" && exec "$commitmsg" ${1+"$@"}
 :
diff --git a/templates/hooks--pre-applypatch.sample b/templates/hooks--pre-applypatch.sample
index b1f187c..4142082 100755
--- a/templates/hooks--pre-applypatch.sample
+++ b/templates/hooks--pre-applypatch.sample
@@ -9,6 +9,6 @@
 # To enable this hook, rename this file to "pre-applypatch".
 
 . git-sh-setup
-test -x "$GIT_DIR/hooks/pre-commit" &&
-	exec "$GIT_DIR/hooks/pre-commit" ${1+"$@"}
+precommit="$(git rev-parse --git-path hooks/pre-commit)"
+test -x "$precommit" && exec "$precommit" ${1+"$@"}
 :
-- 
1.9.1.346.ga2b5940

[PATCH v6 16/32] git-stash: avoid hardcoding $GIT_DIR/logs/....

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 git-stash.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/git-stash.sh b/git-stash.sh
index 393e1ec..41f8f6b 100755
--- a/git-stash.sh
+++ b/git-stash.sh
@@ -184,7 +184,7 @@ store_stash () {
 	fi
 
 	# Make sure the reflog for stash is kept.
-	: >>"$GIT_DIR/logs/$ref_stash"
+	: >>"$(git rev-parse --git-path logs/$ref_stash)"
 	git update-ref -m "$stash_msg" $ref_stash $w_commit
 	ret=$?
 	test $ret != 0 && test -z $quiet &&
@@ -259,7 +259,7 @@ save_stash () {
 		say "$(gettext "No local changes to save")"
 		exit 0
 	fi
-	test -f "$GIT_DIR/logs/$ref_stash" ||
+	test -f "$(git rev-parse --git-path logs/$ref_stash)" ||
 		clear_stash || die "$(gettext "Cannot initialize stash")"
 
 	create_stash "$stash_msg" $untracked
-- 
1.9.1.346.ga2b5940

[PATCH v6 17/32] setup.c: convert is_git_directory() to use strbuf

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 setup.c | 37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/setup.c b/setup.c
index 0a22f8b..425fd79 100644
--- a/setup.c
+++ b/setup.c
@@ -238,31 +238,36 @@ void verify_non_filename(const char *prefix, const char *arg)
  */
 int is_git_directory(const char *suspect)
 {
-	char path[PATH_MAX];
-	size_t len = strlen(suspect);
+	struct strbuf path = STRBUF_INIT;
+	int ret = 0;
+	size_t len;
 
-	if (PATH_MAX <= len + strlen("/objects"))
-		die("Too long path: %.*s", 60, suspect);
-	strcpy(path, suspect);
+	strbuf_addstr(&path, suspect);
+	len = path.len;
 	if (getenv(DB_ENVIRONMENT)) {
 		if (access(getenv(DB_ENVIRONMENT), X_OK))
-			return 0;
+			goto done;
 	}
 	else {
-		strcpy(path + len, "/objects");
-		if (access(path, X_OK))
-			return 0;
+		strbuf_addstr(&path, "/objects");
+		if (access(path.buf, X_OK))
+			goto done;
 	}
 
-	strcpy(path + len, "/refs");
-	if (access(path, X_OK))
-		return 0;
+	strbuf_setlen(&path, len);
+	strbuf_addstr(&path, "/refs");
+	if (access(path.buf, X_OK))
+		goto done;
 
-	strcpy(path + len, "/HEAD");
-	if (validate_headref(path))
-		return 0;
+	strbuf_setlen(&path, len);
+	strbuf_addstr(&path, "/HEAD");
+	if (validate_headref(path.buf))
+		goto done;
 
-	return 1;
+	ret = 1;
+done:
+	strbuf_release(&path);
+	return ret;
 }
 
 int is_inside_git_dir(void)
-- 
1.9.1.346.ga2b5940

[PATCH v6 18/32] setup.c: detect $GIT_COMMON_DIR in is_git_directory()

[Nguyễn Thái Ngọc Duy]

If the file "$GIT_DIR/commondir" exists, it contains the value of
$GIT_COMMON_DIR.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/gitrepository-layout.txt |  7 ++++++
 setup.c                                | 43 +++++++++++++++++++++++++++++-----
 2 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
index 7629e38..0f341fc 100644
--- a/Documentation/gitrepository-layout.txt
+++ b/Documentation/gitrepository-layout.txt
@@ -237,6 +237,13 @@ shallow::
 	file is ignored if $GIT_COMMON_DIR is set and
 	"$GIT_COMMON_DIR/shallow" will be used instead.
 
+commondir::
+	If this file exists, $GIT_COMMON_DIR (see linkgit:git[1]) will
+	be set to the path specified in this file if it is not
+	explicitly set. If the specified path is relative, it is
+	relative to $GIT_DIR. The repository with commondir is
+	incomplete without the repository pointed by "commondir".
+
 modules::
 	Contains the git-repositories of the submodules. This
 	directory is ignored if $GIT_COMMON_DIR is set and
diff --git a/setup.c b/setup.c
index 425fd79..176d505 100644
--- a/setup.c
+++ b/setup.c
@@ -224,6 +224,33 @@ void verify_non_filename(const char *prefix, const char *arg)
 	    "'git <command> [<revision>...] -- [<file>...]'", arg);
 }
 
+static void get_common_dir(struct strbuf *sb, const char *gitdir)
+{
+	struct strbuf data = STRBUF_INIT;
+	struct strbuf path = STRBUF_INIT;
+	const char *git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
+	if (git_common_dir) {
+		strbuf_addstr(sb, git_common_dir);
+		return;
+	}
+	strbuf_addf(&path, "%s/commondir", gitdir);
+	if (file_exists(path.buf)) {
+		if (strbuf_read_file(&data, path.buf, 0) <= 0)
+			die_errno(_("failed to read %s"), path.buf);
+		while (data.len && (data.buf[data.len - 1] == '\n' ||
+				    data.buf[data.len - 1] == '\r'))
+			data.len--;
+		data.buf[data.len] = '\0';
+		strbuf_reset(&path);
+		if (!is_absolute_path(data.buf))
+			strbuf_addf(&path, "%s/", gitdir);
+		strbuf_addbuf(&path, &data);
+		strbuf_addstr(sb, real_path(path.buf));
+	} else
+		strbuf_addstr(sb, gitdir);
+	strbuf_release(&data);
+	strbuf_release(&path);
+}
 
 /*
  * Test if it looks like we're at a git directory.
@@ -242,13 +269,22 @@ int is_git_directory(const char *suspect)
 	int ret = 0;
 	size_t len;
 
-	strbuf_addstr(&path, suspect);
+	/* Check worktree-related signatures */
+	strbuf_addf(&path, "%s/HEAD", suspect);
+	if (validate_headref(path.buf))
+		goto done;
+
+	strbuf_reset(&path);
+	get_common_dir(&path, suspect);
 	len = path.len;
+
+	/* Check non-worktree-related signatures */
 	if (getenv(DB_ENVIRONMENT)) {
 		if (access(getenv(DB_ENVIRONMENT), X_OK))
 			goto done;
 	}
 	else {
+		strbuf_setlen(&path, len);
 		strbuf_addstr(&path, "/objects");
 		if (access(path.buf, X_OK))
 			goto done;
@@ -259,11 +295,6 @@ int is_git_directory(const char *suspect)
 	if (access(path.buf, X_OK))
 		goto done;
 
-	strbuf_setlen(&path, len);
-	strbuf_addstr(&path, "/HEAD");
-	if (validate_headref(path.buf))
-		goto done;
-
 	ret = 1;
 done:
 	strbuf_release(&path);
-- 
1.9.1.346.ga2b5940

[PATCH v6 19/32] setup.c: convert check_repository_format_gently to use strbuf

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 setup.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/setup.c b/setup.c
index 176d505..a17389f 100644
--- a/setup.c
+++ b/setup.c
@@ -342,7 +342,9 @@ void setup_work_tree(void)
 
 static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 {
-	char repo_config[PATH_MAX+1];
+	struct strbuf sb = STRBUF_INIT;
+	const char *repo_config;
+	int ret = 0;
 
 	/*
 	 * git_config() can't be used here because it calls git_pathdup()
@@ -353,7 +355,8 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 	 * Use a gentler version of git_config() to check if this repo
 	 * is a good one.
 	 */
-	snprintf(repo_config, PATH_MAX, "%s/config", gitdir);
+	strbuf_addf(&sb, "%s/config", gitdir);
+	repo_config = sb.buf;
 	git_config_early(check_repository_format_version, NULL, repo_config);
 	if (GIT_REPO_VERSION < repository_format_version) {
 		if (!nongit_ok)
@@ -363,9 +366,10 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 			GIT_REPO_VERSION, repository_format_version);
 		warning("Please upgrade Git");
 		*nongit_ok = -1;
-		return -1;
+		ret = -1;
 	}
-	return 0;
+	strbuf_release(&sb);
+	return ret;
 }
 
 /*
-- 
1.9.1.346.ga2b5940

[PATCH v6 20/32] setup.c: detect $GIT_COMMON_DIR check_repository_format_gently()

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 setup.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/setup.c b/setup.c
index a17389f..79f79f2 100644
--- a/setup.c
+++ b/setup.c
@@ -346,6 +346,10 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 	const char *repo_config;
 	int ret = 0;
 
+	get_common_dir(&sb, gitdir);
+	strbuf_addstr(&sb, "/config");
+	repo_config = sb.buf;
+
 	/*
 	 * git_config() can't be used here because it calls git_pathdup()
 	 * to get $GIT_CONFIG/config. That call will make setup_git_env()
@@ -355,8 +359,6 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 	 * Use a gentler version of git_config() to check if this repo
 	 * is a good one.
 	 */
-	strbuf_addf(&sb, "%s/config", gitdir);
-	repo_config = sb.buf;
 	git_config_early(check_repository_format_version, NULL, repo_config);
 	if (GIT_REPO_VERSION < repository_format_version) {
 		if (!nongit_ok)
-- 
1.9.1.346.ga2b5940

[PATCH v6 21/32] setup.c: support multi-checkout repo setup

[Nguyễn Thái Ngọc Duy]

The repo setup procedure is updated to detect $GIT_DIR/commondir and
set $GIT_COMMON_DIR properly.

The core.worktree is ignored when $GIT_COMMON_DIR is set. This is
because the config file is shared in multi-checkout setup, but
checkout directories _are_ different. Making core.worktree effective
in all checkouts mean it's back to a single checkout.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/config.txt        |  2 ++
 Documentation/git-rev-parse.txt |  3 ++
 builtin/rev-parse.c             |  4 +++
 cache.h                         |  1 +
 environment.c                   |  8 ++---
 setup.c                         | 33 +++++++++++++-----
 t/t1501-worktree.sh             | 76 +++++++++++++++++++++++++++++++++++++++++
 t/t1510-repo-setup.sh           |  1 +
 trace.c                         |  1 +
 9 files changed, 115 insertions(+), 14 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 1d718bd..286e539 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -380,6 +380,8 @@ false), while all other repositories are assumed to be bare (bare
 
 core.worktree::
 	Set the path to the root of the working tree.
+	If GIT_COMMON_DIR environment variable is set, core.worktree
+	is ignored and not used for determining the root of working tree.
 	This can be overridden by the GIT_WORK_TREE environment
 	variable and the '--work-tree' command-line option.
 	The value can be an absolute path or relative to the path to
diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index 9465399..f1867d3 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -215,6 +215,9 @@ If `$GIT_DIR` is not defined and the current directory
 is not detected to lie in a Git repository or work tree
 print a message to stderr and exit with nonzero status.
 
+--git-common-dir::
+	Show `$GIT_COMMON_DIR` if defined, else `$GIT_DIR`.
+
 --is-inside-git-dir::
 	When the current working directory is below the repository
 	directory print "true", otherwise "false".
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 7606d43..29475c5 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -757,6 +757,10 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				printf("%s%s.git\n", cwd, len && cwd[len-1] != '/' ? "/" : "");
 				continue;
 			}
+			if (!strcmp(arg, "--git-common-dir")) {
+				puts(get_git_common_dir());
+				continue;
+			}
 			if (!strcmp(arg, "--resolve-git-dir")) {
 				const char *gitdir = argv[++i];
 				if (!gitdir)
diff --git a/cache.h b/cache.h
index 8052ddc..e7dd5ce 100644
--- a/cache.h
+++ b/cache.h
@@ -422,6 +422,7 @@ extern char *get_object_directory(void);
 extern char *get_index_file(void);
 extern char *get_graft_file(void);
 extern int set_git_dir(const char *path);
+extern int get_common_dir(struct strbuf *sb, const char *gitdir);
 extern const char *get_git_namespace(void);
 extern const char *strip_namespace(const char *namespaced_ref);
 extern const char *get_git_work_tree(void);
diff --git a/environment.c b/environment.c
index 76eb38c..8865765 100644
--- a/environment.c
+++ b/environment.c
@@ -141,6 +141,7 @@ static char *git_path_from_env(const char *envvar, const char *git_dir,
 
 static void setup_git_env(void)
 {
+	struct strbuf sb = STRBUF_INIT;
 	const char *gitfile;
 	const char *shallow_file;
 
@@ -149,12 +150,9 @@ static void setup_git_env(void)
 		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
 	gitfile = read_gitfile(git_dir);
 	git_dir = xstrdup(gitfile ? gitfile : git_dir);
-	git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
-	if (git_common_dir) {
+	if (get_common_dir(&sb, git_dir))
 		git_common_dir_env = 1;
-		git_common_dir = xstrdup(git_common_dir);
-	} else
-		git_common_dir = git_dir;
+	git_common_dir = strbuf_detach(&sb, NULL);
 	git_object_dir = git_path_from_env(DB_ENVIRONMENT, git_common_dir,
 					   "objects", &git_db_env);
 	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, git_dir,
diff --git a/setup.c b/setup.c
index 79f79f2..8f90bc3 100644
--- a/setup.c
+++ b/setup.c
@@ -224,14 +224,15 @@ void verify_non_filename(const char *prefix, const char *arg)
 	    "'git <command> [<revision>...] -- [<file>...]'", arg);
 }
 
-static void get_common_dir(struct strbuf *sb, const char *gitdir)
+int get_common_dir(struct strbuf *sb, const char *gitdir)
 {
 	struct strbuf data = STRBUF_INIT;
 	struct strbuf path = STRBUF_INIT;
 	const char *git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
+	int ret = 0;
 	if (git_common_dir) {
 		strbuf_addstr(sb, git_common_dir);
-		return;
+		return 1;
 	}
 	strbuf_addf(&path, "%s/commondir", gitdir);
 	if (file_exists(path.buf)) {
@@ -246,10 +247,12 @@ static void get_common_dir(struct strbuf *sb, const char *gitdir)
 			strbuf_addf(&path, "%s/", gitdir);
 		strbuf_addbuf(&path, &data);
 		strbuf_addstr(sb, real_path(path.buf));
+		ret = 1;
 	} else
 		strbuf_addstr(sb, gitdir);
 	strbuf_release(&data);
 	strbuf_release(&path);
+	return ret;
 }
 
 /*
@@ -340,13 +343,26 @@ void setup_work_tree(void)
 	initialized = 1;
 }
 
+static int check_repo_format(const char *var, const char *value, void *cb)
+{
+	if (strcmp(var, "core.repositoryformatversion") == 0)
+		repository_format_version = git_config_int(var, value);
+	else if (strcmp(var, "core.sharedrepository") == 0)
+		shared_repository = git_config_perm(var, value);
+	return 0;
+}
+
 static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 {
 	struct strbuf sb = STRBUF_INIT;
 	const char *repo_config;
+	config_fn_t fn;
 	int ret = 0;
 
-	get_common_dir(&sb, gitdir);
+	if (get_common_dir(&sb, gitdir))
+		fn = check_repo_format;
+	else
+		fn = check_repository_format_version;
 	strbuf_addstr(&sb, "/config");
 	repo_config = sb.buf;
 
@@ -359,7 +375,7 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 	 * Use a gentler version of git_config() to check if this repo
 	 * is a good one.
 	 */
-	git_config_early(check_repository_format_version, NULL, repo_config);
+	git_config_early(fn, NULL, repo_config);
 	if (GIT_REPO_VERSION < repository_format_version) {
 		if (!nongit_ok)
 			die ("Expected git repo version <= %d, found %d",
@@ -831,11 +847,10 @@ int git_config_perm(const char *var, const char *value)
 
 int check_repository_format_version(const char *var, const char *value, void *cb)
 {
-	if (strcmp(var, "core.repositoryformatversion") == 0)
-		repository_format_version = git_config_int(var, value);
-	else if (strcmp(var, "core.sharedrepository") == 0)
-		shared_repository = git_config_perm(var, value);
-	else if (strcmp(var, "core.bare") == 0) {
+	int ret = check_repo_format(var, value, cb);
+	if (ret)
+		return ret;
+	if (strcmp(var, "core.bare") == 0) {
 		is_bare_repository_cfg = git_config_bool(var, value);
 		if (is_bare_repository_cfg == 1)
 			inside_work_tree = -1;
diff --git a/t/t1501-worktree.sh b/t/t1501-worktree.sh
index 8f36aa9..e6ac7a4 100755
--- a/t/t1501-worktree.sh
+++ b/t/t1501-worktree.sh
@@ -346,4 +346,80 @@ test_expect_success 'relative $GIT_WORK_TREE and git subprocesses' '
 	test_cmp expected actual
 '
 
+test_expect_success 'Multi-worktree setup' '
+	mkdir work &&
+	mkdir -p repo.git/repos/foo &&
+	cp repo.git/HEAD repo.git/index repo.git/repos/foo &&
+	sane_unset GIT_DIR GIT_CONFIG GIT_WORK_TREE
+'
+
+test_expect_success 'GIT_DIR set (1)' '
+	echo "gitdir: repo.git/repos/foo" >gitfile &&
+	echo ../.. >repo.git/repos/foo/commondir &&
+	(
+		cd work &&
+		GIT_DIR=../gitfile git rev-parse --git-common-dir >actual &&
+		test-path-utils real_path "$TRASH_DIRECTORY/repo.git" >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'GIT_DIR set (2)' '
+	echo "gitdir: repo.git/repos/foo" >gitfile &&
+	echo "$TRASH_DIRECTORY/repo.git" >repo.git/repos/foo/commondir &&
+	(
+		cd work &&
+		GIT_DIR=../gitfile git rev-parse --git-common-dir >actual &&
+		test-path-utils real_path "$TRASH_DIRECTORY/repo.git" >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'Auto discovery' '
+	echo "gitdir: repo.git/repos/foo" >.git &&
+	echo ../.. >repo.git/repos/foo/commondir &&
+	(
+		cd work &&
+		git rev-parse --git-common-dir >actual &&
+		test-path-utils real_path "$TRASH_DIRECTORY/repo.git" >expect &&
+		test_cmp expect actual &&
+		echo haha >data1 &&
+		git add data1 &&
+		git ls-files --full-name :/ | grep data1 >actual &&
+		echo work/data1 >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success '$GIT_DIR/common overrides core.worktree' '
+	mkdir elsewhere &&
+	git --git-dir=repo.git config core.worktree "$TRASH_DIRECTORY/elsewhere" &&
+	echo "gitdir: repo.git/repos/foo" >.git &&
+	echo ../.. >repo.git/repos/foo/commondir &&
+	(
+		cd work &&
+		git rev-parse --git-common-dir >actual &&
+		test-path-utils real_path "$TRASH_DIRECTORY/repo.git" >expect &&
+		test_cmp expect actual &&
+		echo haha >data2 &&
+		git add data2 &&
+		git ls-files --full-name :/ | grep data2 >actual &&
+		echo work/data2 >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success '$GIT_WORK_TREE overrides $GIT_DIR/common' '
+	echo "gitdir: repo.git/repos/foo" >.git &&
+	echo ../.. >repo.git/repos/foo/commondir &&
+	(
+		cd work &&
+		echo haha >data3 &&
+		git --git-dir=../.git --work-tree=. add data3 &&
+		git ls-files --full-name -- :/ | grep data3 >actual &&
+		echo data3 >expect &&
+		test_cmp expect actual
+	)
+'
+
 test_done
diff --git a/t/t1510-repo-setup.sh b/t/t1510-repo-setup.sh
index e1b2a99..33c1a58 100755
--- a/t/t1510-repo-setup.sh
+++ b/t/t1510-repo-setup.sh
@@ -106,6 +106,7 @@ setup_env () {
 expect () {
 	cat >"$1/expected" <<-EOF
 	setup: git_dir: $2
+	setup: git_common_dir: $2
 	setup: worktree: $3
 	setup: cwd: $4
 	setup: prefix: $5
diff --git a/trace.c b/trace.c
index 08180a9..a594761 100644
--- a/trace.c
+++ b/trace.c
@@ -173,6 +173,7 @@ void trace_repo_setup(const char *prefix)
 		prefix = "(null)";
 
 	trace_printf_key(key, "setup: git_dir: %s\n", quote_crnl(get_git_dir()));
+	trace_printf_key(key, "setup: git_common_dir: %s\n", quote_crnl(get_git_common_dir()));
 	trace_printf_key(key, "setup: worktree: %s\n", quote_crnl(git_work_tree));
 	trace_printf_key(key, "setup: cwd: %s\n", quote_crnl(cwd));
 	trace_printf_key(key, "setup: prefix: %s\n", quote_crnl(prefix));
-- 
1.9.1.346.ga2b5940

[PATCH v6 22/32] wrapper.c: wrapper to open a file, fprintf then close

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 cache.h   |  2 ++
 wrapper.c | 31 +++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/cache.h b/cache.h
index e7dd5ce..b363c00 100644
--- a/cache.h
+++ b/cache.h
@@ -1355,6 +1355,8 @@ static inline ssize_t write_str_in_full(int fd, const char *str)
 {
 	return write_in_full(fd, str, strlen(str));
 }
+__attribute__((format (printf,3,4)))
+extern int write_file(const char *path, int fatal, const char *fmt, ...);
 
 /* pager.c */
 extern void setup_pager(void);
diff --git a/wrapper.c b/wrapper.c
index bc1bfb8..9d7b9ac 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -493,3 +493,34 @@ struct passwd *xgetpwuid_self(void)
 		    errno ? strerror(errno) : _("no such user"));
 	return pw;
 }
+
+int write_file(const char *path, int fatal, const char *fmt, ...)
+{
+	struct strbuf sb = STRBUF_INIT;
+	va_list params;
+	int fd = open(path, O_RDWR | O_CREAT | O_TRUNC, 0666);
+	if (fd < 0) {
+		if (fatal)
+			die_errno(_("could not open %s for writing"), path);
+		return -1;
+	}
+	va_start(params, fmt);
+	strbuf_vaddf(&sb, fmt, params);
+	va_end(params);
+	if (write_in_full(fd, sb.buf, sb.len) != sb.len) {
+		int err = errno;
+		close(fd);
+		strbuf_release(&sb);
+		errno = err;
+		if (fatal)
+			die_errno(_("could not write to %s"), path);
+		return -1;
+	}
+	strbuf_release(&sb);
+	if (close(fd)) {
+		if (fatal)
+			die_errno(_("could not close %s"), path);
+		return -1;
+	}
+	return 0;
+}
-- 
1.9.1.346.ga2b5940

[PATCH v6 23/32] use new wrapper write_file() for simple file writing

[Nguyễn Thái Ngọc Duy]

This fixes common problems in these code about error handling,
forgetting to close the file handle after fprintf() fails, or not
printing out the error string..

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/branch.c  |  4 +---
 builtin/init-db.c |  7 +------
 daemon.c          | 11 +----------
 submodule.c       |  9 ++-------
 transport.c       |  8 +++-----
 5 files changed, 8 insertions(+), 31 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index 652b1d2..2d1c57c 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -754,7 +754,6 @@ static const char edit_description[] = "BRANCH_DESCRIPTION";
 
 static int edit_branch_description(const char *branch_name)
 {
-	FILE *fp;
 	int status;
 	struct strbuf buf = STRBUF_INIT;
 	struct strbuf name = STRBUF_INIT;
@@ -767,8 +766,7 @@ static int edit_branch_description(const char *branch_name)
 		    "  %s\n"
 		    "Lines starting with '%c' will be stripped.\n",
 		    branch_name, comment_line_char);
-	fp = fopen(git_path(edit_description), "w");
-	if ((fwrite(buf.buf, 1, buf.len, fp) < buf.len) || fclose(fp)) {
+	if (write_file(git_path(edit_description), 0, "%s", buf.buf)) {
 		strbuf_release(&buf);
 		return error(_("could not write branch description template: %s"),
 			     strerror(errno));
diff --git a/builtin/init-db.c b/builtin/init-db.c
index 56f85e2..ce8416a 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -342,7 +342,6 @@ int set_git_dir_init(const char *git_dir, const char *real_git_dir,
 static void separate_git_dir(const char *git_dir)
 {
 	struct stat st;
-	FILE *fp;
 
 	if (!stat(git_link, &st)) {
 		const char *src;
@@ -358,11 +357,7 @@ static void separate_git_dir(const char *git_dir)
 			die_errno(_("unable to move %s to %s"), src, git_dir);
 	}
 
-	fp = fopen(git_link, "w");
-	if (!fp)
-		die(_("Could not create git link %s"), git_link);
-	fprintf(fp, "gitdir: %s\n", git_dir);
-	fclose(fp);
+	write_file(git_link, 1, "gitdir: %s\n", git_dir);
 }
 
 int init_db(const char *template_dir, unsigned int flags)
diff --git a/daemon.c b/daemon.c
index f9c63e9..40d0297 100644
--- a/daemon.c
+++ b/daemon.c
@@ -1091,15 +1091,6 @@ static struct credentials *prepare_credentials(const char *user_name,
 }
 #endif
 
-static void store_pid(const char *path)
-{
-	FILE *f = fopen(path, "w");
-	if (!f)
-		die_errno("cannot open pid file '%s'", path);
-	if (fprintf(f, "%"PRIuMAX"\n", (uintmax_t) getpid()) < 0 || fclose(f) != 0)
-		die_errno("failed to write pid file '%s'", path);
-}
-
 static int serve(struct string_list *listen_addr, int listen_port,
     struct credentials *cred)
 {
@@ -1309,7 +1300,7 @@ int main(int argc, char **argv)
 		sanitize_stdfds();
 
 	if (pid_file)
-		store_pid(pid_file);
+		write_file(pid_file, 1, "%"PRIuMAX"\n", (uintmax_t) getpid());
 
 	/* prepare argv for serving-processes */
 	cld_argv = xmalloc(sizeof (char *) * (argc + 2));
diff --git a/submodule.c b/submodule.c
index b80ecac..b7b6059 100644
--- a/submodule.c
+++ b/submodule.c
@@ -1112,16 +1112,11 @@ void connect_work_tree_and_git_dir(const char *work_tree, const char *git_dir)
 	struct strbuf file_name = STRBUF_INIT;
 	struct strbuf rel_path = STRBUF_INIT;
 	const char *real_work_tree = xstrdup(real_path(work_tree));
-	FILE *fp;
 
 	/* Update gitfile */
 	strbuf_addf(&file_name, "%s/.git", work_tree);
-	fp = fopen(file_name.buf, "w");
-	if (!fp)
-		die(_("Could not create git link %s"), file_name.buf);
-	fprintf(fp, "gitdir: %s\n", relative_path(git_dir, real_work_tree,
-						  &rel_path));
-	fclose(fp);
+	write_file(file_name.buf, 1, "gitdir: %s\n",
+		   relative_path(git_dir, real_work_tree, &rel_path));
 
 	/* Update core.worktree setting */
 	strbuf_reset(&file_name);
diff --git a/transport.c b/transport.c
index 325f03e..172b3d8 100644
--- a/transport.c
+++ b/transport.c
@@ -294,7 +294,6 @@ static int write_one_ref(const char *name, const unsigned char *sha1,
 {
 	struct strbuf *buf = data;
 	int len = buf->len;
-	FILE *f;
 
 	/* when called via for_each_ref(), flags is non-zero */
 	if (flags && !starts_with(name, "refs/heads/") &&
@@ -303,10 +302,9 @@ static int write_one_ref(const char *name, const unsigned char *sha1,
 
 	strbuf_addstr(buf, name);
 	if (safe_create_leading_directories(buf->buf) ||
-			!(f = fopen(buf->buf, "w")) ||
-			fprintf(f, "%s\n", sha1_to_hex(sha1)) < 0 ||
-			fclose(f))
-		return error("problems writing temporary file %s", buf->buf);
+	    write_file(buf->buf, 0, "%s\n", sha1_to_hex(sha1)))
+		return error("problems writing temporary file %s: %s",
+			     buf->buf, strerror(errno));
 	strbuf_setlen(buf, len);
 	return 0;
 }
-- 
1.9.1.346.ga2b5940

[PATCH v6 24/32] checkout: support checking out into a new working directory

[Nguyễn Thái Ngọc Duy]

"git checkout --to" sets up a new working directory with a .git file
pointing to $GIT_DIR/repos/<id>. It then executes "git checkout" again
on the new worktree with the same arguments except "--to" is taken
out. The second checkout execution, which is not contaminated with any
info from the current repository, will actually check out and
everything that normal "git checkout" does.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git-checkout.txt         | 34 +++++++++++++
 Documentation/git.txt                  |  3 +-
 Documentation/gitrepository-layout.txt |  7 +++
 builtin/checkout.c                     | 93 +++++++++++++++++++++++++++++++++-
 path.c                                 |  2 +-
 t/t2025-checkout-to.sh (new +x)        | 48 ++++++++++++++++++
 6 files changed, 183 insertions(+), 4 deletions(-)
 create mode 100755 t/t2025-checkout-to.sh

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 33ad2ad..fcf73b2 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -225,6 +225,13 @@ This means that you can use `git checkout -p` to selectively discard
 edits from your current working tree. See the ``Interactive Mode''
 section of linkgit:git-add[1] to learn how to operate the `--patch` mode.
 
+--to=<path>::
+	Check out a new branch in a separate working directory at
+	`<path>`. A new working directory is linked to the current
+	repository, sharing everything except working directory
+	specific files such as HEAD, index... See "MULTIPLE CHECKOUT
+	MODE" section for more information.
+
 <branch>::
 	Branch to checkout; if it refers to a branch (i.e., a name that,
 	when prepended with "refs/heads/", is a valid ref), then that
@@ -388,6 +395,33 @@ $ git reflog -2 HEAD # or
 $ git log -g -2 HEAD
 ------------
 
+MULTIPLE CHECKOUT MODE
+-------------------------------
+Normally a working directory is attached to repository. When "git
+checkout --to" is used, a new working directory is attached to the
+current repository. This new working directory is called "linked
+checkout" as compared to the "main checkout" prepared by "git init" or
+"git clone". A repository has one main checkout and zero or more
+linked checkouts.
+
+All checkouts share the same repository. Linked checkouts see the
+repository a bit different from the main checkout. When the checkout
+"new" reads the path $GIT_DIR/HEAD for example, the actual path
+returned could be $GIT_DIR/repos/new/HEAD. This ensures checkouts
+won't step on each other.
+
+Each linked checkout has a private space in $GIT_DIR/repos, usually
+named after the base name of the working directory with a number added
+to make it unique. The linked checkout's $GIT_DIR points to this
+private space while $GIT_COMMON_DIR points to the main checkout's
+$GIT_DIR. These settings are done by "git checkout --to".
+
+Because in this mode $GIT_DIR becomes a lightweight virtual file
+system where a path could be rewritten to some place else, accessing
+$GIT_DIR from scripts should use `git rev-parse --git-path` to resolve
+a path instead of using it directly unless the path is known to be
+private to the working directory.
+
 EXAMPLES
 --------
 
diff --git a/Documentation/git.txt b/Documentation/git.txt
index 749052f..c0a4940 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -792,7 +792,8 @@ Git so take care if using Cogito etc.
 	If this variable is set to a path, non-worktree files that are
 	normally in $GIT_DIR will be taken from this path
 	instead. Worktree-specific files such as HEAD or index are
-	taken from $GIT_DIR. See linkgit:gitrepository-layout[5] for
+	taken from $GIT_DIR. See linkgit:gitrepository-layout[5] and
+	the section 'MULTIPLE CHECKOUT MODE' in linkgit:checkout[1]
 	details. This variable has lower precedence than other path
 	variables such as GIT_INDEX_FILE, GIT_OBJECT_DIRECTORY...
 
diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
index 0f341fc..543d874 100644
--- a/Documentation/gitrepository-layout.txt
+++ b/Documentation/gitrepository-layout.txt
@@ -249,6 +249,13 @@ modules::
 	directory is ignored if $GIT_COMMON_DIR is set and
 	"$GIT_COMMON_DIR/modules" will be used instead.
 
+repos::
+	Contains worktree specific information of linked
+	checkouts. Each subdirectory contains the worktree-related
+	part of a linked checkout. This directory is ignored
+	$GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/repos" will be
+	used instead.
+
 SEE ALSO
 --------
 linkgit:git-init[1],
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 7356799..7df586a 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -48,6 +48,10 @@ struct checkout_opts {
 	const char *prefix;
 	struct pathspec pathspec;
 	struct tree *source_tree;
+
+	const char *new_worktree;
+	const char **saved_argv;
+	int new_worktree_mode;
 };
 
 static int post_checkout_hook(struct commit *old, struct commit *new,
@@ -250,6 +254,9 @@ static int checkout_paths(const struct checkout_opts *opts,
 		die(_("Cannot update paths and switch to branch '%s' at the same time."),
 		    opts->new_branch);
 
+	if (opts->new_worktree)
+		die(_("'%s' cannot be used with updating paths"), "--to");
+
 	if (opts->patch_mode)
 		return run_add_interactive(revision, "--patch=checkout",
 					   &opts->pathspec);
@@ -485,7 +492,7 @@ static int merge_working_tree(const struct checkout_opts *opts,
 			topts.dir->flags |= DIR_SHOW_IGNORED;
 			setup_standard_excludes(topts.dir);
 		}
-		tree = parse_tree_indirect(old->commit ?
+		tree = parse_tree_indirect(old->commit && !opts->new_worktree_mode ?
 					   old->commit->object.sha1 :
 					   EMPTY_TREE_SHA1_BIN);
 		init_tree_desc(&trees[0], tree->buffer, tree->size);
@@ -796,7 +803,8 @@ static int switch_branches(const struct checkout_opts *opts,
 		return ret;
 	}
 
-	if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
+	if (!opts->quiet && !old.path && old.commit &&
+	    new->commit != old.commit && !opts->new_worktree_mode)
 		orphaned_commit_warning(old.commit, new->commit);
 
 	update_refs_for_switch(opts, &old, new);
@@ -806,6 +814,74 @@ static int switch_branches(const struct checkout_opts *opts,
 	return ret || writeout_error;
 }
 
+static int prepare_linked_checkout(const struct checkout_opts *opts,
+				   struct branch_info *new)
+{
+	struct strbuf sb_git = STRBUF_INIT, sb_repo = STRBUF_INIT;
+	struct strbuf sb = STRBUF_INIT;
+	const char *path = opts->new_worktree, *name;
+	struct stat st;
+	struct child_process cp;
+	int counter = 0, len;
+
+	if (!new->commit)
+		die(_("no branch specified"));
+
+	len = strlen(path);
+	while (len && is_dir_sep(path[len - 1]))
+		len--;
+
+	for (name = path + len - 1; name > path; name--)
+		if (is_dir_sep(*name)) {
+			name++;
+			break;
+		}
+	strbuf_addstr(&sb_repo,
+		      git_path("repos/%.*s", (int)(path + len - name), name));
+	len = sb_repo.len;
+	if (safe_create_leading_directories_const(sb_repo.buf))
+		die_errno(_("could not create leading directories of '%s'"),
+			  sb_repo.buf);
+	while (!stat(sb_repo.buf, &st)) {
+		counter++;
+		strbuf_setlen(&sb_repo, len);
+		strbuf_addf(&sb_repo, "%d", counter);
+	}
+	name = strrchr(sb_repo.buf, '/') + 1;
+	if (mkdir(sb_repo.buf, 0777))
+		die_errno(_("could not create directory of '%s'"), sb_repo.buf);
+
+	strbuf_addf(&sb_git, "%s/.git", path);
+	if (safe_create_leading_directories_const(sb_git.buf))
+		die_errno(_("could not create leading directories of '%s'"),
+			  sb_git.buf);
+
+	write_file(sb_git.buf, 1, "gitdir: %s/repos/%s\n",
+		   real_path(get_git_common_dir()), name);
+	/*
+	 * This is to keep resolve_ref() happy. We need a valid HEAD
+	 * or is_git_directory() will reject the directory. Any valid
+	 * value would do because this value will be ignored and
+	 * replaced at the next (real) checkout.
+	 */
+	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
+	write_file(sb.buf, 1, "%s\n", sha1_to_hex(new->commit->object.sha1));
+	strbuf_reset(&sb);
+	strbuf_addf(&sb, "%s/commondir", sb_repo.buf);
+	write_file(sb.buf, 1, "../..\n");
+
+	if (!opts->quiet)
+		fprintf_ln(stderr, _("Enter %s (identifier %s)"), path, name);
+
+	setenv("GIT_CHECKOUT_NEW_WORKTREE", "1", 1);
+	setenv(GIT_DIR_ENVIRONMENT, sb_git.buf, 1);
+	setenv(GIT_WORK_TREE_ENVIRONMENT, path, 1);
+	memset(&cp, 0, sizeof(cp));
+	cp.git_cmd = 1;
+	cp.argv = opts->saved_argv;
+	return run_command(&cp);
+}
+
 static int git_checkout_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "diff.ignoresubmodules")) {
@@ -1067,6 +1143,9 @@ static int checkout_branch(struct checkout_opts *opts,
 		die(_("Cannot switch branch to a non-commit '%s'"),
 		    new->name);
 
+	if (opts->new_worktree)
+		return prepare_linked_checkout(opts, new);
+
 	if (!new->commit && opts->new_branch) {
 		unsigned char rev[20];
 		int flag;
@@ -1109,6 +1188,8 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 			 N_("do not limit pathspecs to sparse entries only")),
 		OPT_HIDDEN_BOOL(0, "guess", &dwim_new_local_branch,
 				N_("second guess 'git checkout no-such-branch'")),
+		OPT_STRING(0, "to", &opts.new_worktree, N_("path"),
+			   N_("check a branch out in a separate working directory")),
 		OPT_END(),
 	};
 
@@ -1117,6 +1198,9 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	opts.overwrite_ignore = 1;
 	opts.prefix = prefix;
 
+	opts.saved_argv = xmalloc(sizeof(const char *) * (argc + 2));
+	memcpy(opts.saved_argv, argv, sizeof(const char *) * (argc + 1));
+
 	gitmodules_config();
 	git_config(git_checkout_config, &opts);
 
@@ -1125,6 +1209,11 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
 
+	/* recursive execution from checkout_new_worktree() */
+	opts.new_worktree_mode = getenv("GIT_CHECKOUT_NEW_WORKTREE") != NULL;
+	if (opts.new_worktree_mode)
+		opts.new_worktree = NULL;
+
 	if (conflict_style) {
 		opts.merge = 1; /* implied */
 		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
diff --git a/path.c b/path.c
index 8a6586c..e41d6b3 100644
--- a/path.c
+++ b/path.c
@@ -92,7 +92,7 @@ static void replace_dir(struct strbuf *buf, int len, const char *newdir)
 
 static const char *common_list[] = {
 	"/branches", "/hooks", "/info", "/logs", "/lost-found", "/modules",
-	"/objects", "/refs", "/remotes", "/rr-cache", "/svn",
+	"/objects", "/refs", "/remotes", "/repos", "/rr-cache", "/svn",
 	"config", "gc.pid", "packed-refs", "shallow",
 	NULL
 };
diff --git a/t/t2025-checkout-to.sh b/t/t2025-checkout-to.sh
new file mode 100755
index 0000000..5ec49e2
--- /dev/null
+++ b/t/t2025-checkout-to.sh
@@ -0,0 +1,48 @@
+#!/bin/sh
+
+test_description='test git checkout --to'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit init
+'
+
+test_expect_success 'checkout --to not updating paths' '
+	test_must_fail git checkout --to -- init.t
+'
+
+test_expect_success 'checkout --to a new worktree' '
+	git checkout --to here master &&
+	(
+		cd here &&
+		test_cmp ../init.t init.t &&
+		git symbolic-ref HEAD >actual &&
+		echo refs/heads/master >expect &&
+		test_cmp expect actual &&
+		git fsck
+	)
+'
+
+test_expect_success 'checkout --to from a linked checkout' '
+	(
+		cd here &&
+		git checkout --to nested-here master
+		cd nested-here &&
+		git fsck
+	)
+'
+
+test_expect_success 'checkout --to a new worktree creating new branch' '
+	git checkout --to there -b newmaster master &&
+	(
+		cd there &&
+		test_cmp ../init.t init.t &&
+		git symbolic-ref HEAD >actual &&
+		echo refs/heads/newmaster >expect &&
+		test_cmp expect actual &&
+		git fsck
+	)
+'
+
+test_done
-- 
1.9.1.346.ga2b5940

[PATCH v6 25/32] checkout: clean up half-prepared directories in --to mode

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/checkout.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 7df586a..5a52da4 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -20,6 +20,7 @@
 #include "resolve-undo.h"
 #include "submodule.h"
 #include "argv-array.h"
+#include "sigchain.h"
 
 static const char * const checkout_usage[] = {
 	N_("git checkout [options] <branch>"),
@@ -814,6 +815,35 @@ static int switch_branches(const struct checkout_opts *opts,
 	return ret || writeout_error;
 }
 
+static const char *junk_work_tree;
+static const char *junk_git_dir;
+static int is_junk;
+static pid_t junk_pid;
+
+static void remove_junk(void)
+{
+	struct strbuf sb = STRBUF_INIT;
+	if (!is_junk || getpid() != junk_pid)
+		return;
+	if (junk_git_dir) {
+		strbuf_addstr(&sb, junk_git_dir);
+		remove_dir_recursively(&sb, 0);
+		strbuf_reset(&sb);
+	}
+	if (junk_work_tree) {
+		strbuf_addstr(&sb, junk_work_tree);
+		remove_dir_recursively(&sb, 0);
+	}
+	strbuf_release(&sb);
+}
+
+static void remove_junk_on_signal(int signo)
+{
+	remove_junk();
+	sigchain_pop(signo);
+	raise(signo);
+}
+
 static int prepare_linked_checkout(const struct checkout_opts *opts,
 				   struct branch_info *new)
 {
@@ -822,7 +852,7 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	const char *path = opts->new_worktree, *name;
 	struct stat st;
 	struct child_process cp;
-	int counter = 0, len;
+	int counter = 0, len, ret;
 
 	if (!new->commit)
 		die(_("no branch specified"));
@@ -848,13 +878,21 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 		strbuf_addf(&sb_repo, "%d", counter);
 	}
 	name = strrchr(sb_repo.buf, '/') + 1;
+
+	junk_pid = getpid();
+	atexit(remove_junk);
+	sigchain_push_common(remove_junk_on_signal);
+
 	if (mkdir(sb_repo.buf, 0777))
 		die_errno(_("could not create directory of '%s'"), sb_repo.buf);
+	junk_git_dir = sb_repo.buf;
+	is_junk = 1;
 
 	strbuf_addf(&sb_git, "%s/.git", path);
 	if (safe_create_leading_directories_const(sb_git.buf))
 		die_errno(_("could not create leading directories of '%s'"),
 			  sb_git.buf);
+	junk_work_tree = path;
 
 	write_file(sb_git.buf, 1, "gitdir: %s/repos/%s\n",
 		   real_path(get_git_common_dir()), name);
@@ -879,7 +917,14 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	memset(&cp, 0, sizeof(cp));
 	cp.git_cmd = 1;
 	cp.argv = opts->saved_argv;
-	return run_command(&cp);
+	ret = run_command(&cp);
+	if (!ret)
+		is_junk = 0;
+	strbuf_release(&sb);
+	strbuf_release(&sb_repo);
+	strbuf_release(&sb_git);
+	return ret;
+
 }
 
 static int git_checkout_config(const char *var, const char *value, void *cb)
-- 
1.9.1.346.ga2b5940

[PATCH v6 26/32] checkout: detach if the branch is already checked out elsewhere

[Nguyễn Thái Ngọc Duy]

The normal rule is anything outside refs/heads/ is detached. This
increases strictness of the rule a bit more: if the branch is checked
out (either in $GIT_COMMON_DIR/HEAD or any $GIT_DIR/repos/.../HEAD)
then it's detached as well.

A hint is given so the user knows where to go and do something there
if they still want to checkout undetached here.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/checkout.c     | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++
 t/t2025-checkout-to.sh | 15 ++++++++--
 2 files changed, 92 insertions(+), 3 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 5a52da4..069e803 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -432,6 +432,11 @@ struct branch_info {
 	const char *name; /* The short name used */
 	const char *path; /* The full name of a real branch */
 	struct commit *commit; /* The named commit */
+	/*
+	 * if not null the branch is detached because it's already
+	 * checked out in this checkout
+	 */
+	char *checkout;
 };
 
 static void setup_branch_path(struct branch_info *branch)
@@ -640,6 +645,11 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
 			if (old->path && advice_detached_head)
 				detach_advice(new->name);
 			describe_detached_head(_("HEAD is now at"), new->commit);
+			if (new->checkout && !*new->checkout)
+				fprintf(stderr, _("hint: the main checkout is holding this branch\n"));
+			else if (new->checkout)
+				fprintf(stderr, _("hint: the linked checkout %s is holding this branch\n"),
+					new->checkout);
 		}
 	} else if (new->path) {	/* Switch branches. */
 		create_symref("HEAD", new->path, msg.buf);
@@ -982,6 +992,73 @@ static const char *unique_tracking_name(const char *name, unsigned char *sha1)
 	return NULL;
 }
 
+static int check_linked_checkout(struct branch_info *new,
+				  const char *name, const char *path)
+{
+	struct strbuf sb = STRBUF_INIT;
+	char *start, *end;
+	if (strbuf_read_file(&sb, path, 0) < 0)
+		return 0;
+	if (!starts_with(sb.buf, "ref:")) {
+		strbuf_release(&sb);
+		return 0;
+	}
+
+	start = sb.buf + 4;
+	while (isspace(*start))
+		start++;
+	end = start;
+	while (*end && !isspace(*end))
+		end++;
+	if (!strncmp(start, new->path, end - start) &&
+	    new->path[end - start] == '\0') {
+		strbuf_release(&sb);
+		new->path = NULL; /* detach */
+		new->checkout = xstrdup(name); /* reason */
+		return 1;
+	}
+	strbuf_release(&sb);
+	return 0;
+}
+
+static void check_linked_checkouts(struct branch_info *new)
+{
+	struct strbuf path = STRBUF_INIT;
+	DIR *dir;
+	struct dirent *d;
+
+	strbuf_addf(&path, "%s/repos", get_git_common_dir());
+	if ((dir = opendir(path.buf)) == NULL) {
+		strbuf_release(&path);
+		return;
+	}
+
+	strbuf_reset(&path);
+	strbuf_addf(&path, "%s/HEAD", get_git_common_dir());
+	/*
+	 * $GIT_COMMON_DIR/HEAD is practically outside
+	 * $GIT_DIR so resolve_ref_unsafe() won't work (it
+	 * uses git_path). Parse the ref ourselves.
+	 */
+	if (check_linked_checkout(new, "", path.buf)) {
+		strbuf_release(&path);
+		closedir(dir);
+		return;
+	}
+
+	while ((d = readdir(dir)) != NULL) {
+		if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
+			continue;
+		strbuf_reset(&path);
+		strbuf_addf(&path, "%s/repos/%s/HEAD",
+			    get_git_common_dir(), d->d_name);
+		if (check_linked_checkout(new, d->d_name, path.buf))
+			break;
+	}
+	strbuf_release(&path);
+	closedir(dir);
+}
+
 static int parse_branchname_arg(int argc, const char **argv,
 				int dwim_new_local_branch_ok,
 				struct branch_info *new,
@@ -1109,6 +1186,9 @@ static int parse_branchname_arg(int argc, const char **argv,
 	else
 		new->path = NULL; /* not an existing branch */
 
+	if (new->path)
+		check_linked_checkouts(new);
+
 	new->commit = lookup_commit_reference_gently(rev, 1);
 	if (!new->commit) {
 		/* not a commit */
diff --git a/t/t2025-checkout-to.sh b/t/t2025-checkout-to.sh
index 5ec49e2..2d35a9b 100755
--- a/t/t2025-checkout-to.sh
+++ b/t/t2025-checkout-to.sh
@@ -13,13 +13,14 @@ test_expect_success 'checkout --to not updating paths' '
 '
 
 test_expect_success 'checkout --to a new worktree' '
+	git rev-parse HEAD >expect &&
 	git checkout --to here master &&
 	(
 		cd here &&
 		test_cmp ../init.t init.t &&
-		git symbolic-ref HEAD >actual &&
-		echo refs/heads/master >expect &&
-		test_cmp expect actual &&
+		test_must_fail git symbolic-ref HEAD &&
+		git rev-parse HEAD >actual &&
+		test_cmp ../expect actual &&
 		git fsck
 	)
 '
@@ -45,4 +46,12 @@ test_expect_success 'checkout --to a new worktree creating new branch' '
 	)
 '
 
+test_expect_success 'detach if the same branch is already checked out' '
+	(
+		cd here &&
+		git checkout newmaster &&
+		test_must_fail git symbolic-ref HEAD
+	)
+'
+
 test_done
-- 
1.9.1.346.ga2b5940

[PATCH v6 27/32] prune: strategies for linked checkouts

[Nguyễn Thái Ngọc Duy]

(alias R=$GIT_COMMON_DIR/repos/<id>)

 - linked checkouts are supposed to keep its location in $R/gitdir up
   to date. The use case is auto fixup after a manual checkout move.

 - linked checkouts are supposed to update mtime of $R/gitdir. If
   $R/gitdir's mtime is older than a limit, and it points to nowhere,
   repos/<id> is to be pruned.

 - If $R/locked exists, repos/<id> is not supposed to be pruned. If
   $R/locked exists and $R/gitdir's mtime is older than a really long
   limit, warn about old unused repo.

 - "git checkout --to" is supposed to make a hard link named $R/link
   pointing to the .git file on supported file systems to help detect
   the user manually deleting the checkout. If $R/link exists and its
   link count is greated than 1, the repo is kept.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git-prune.txt            |  3 ++
 Documentation/gitrepository-layout.txt | 19 +++++++++
 builtin/checkout.c                     | 14 +++++++
 builtin/prune.c                        | 74 ++++++++++++++++++++++++++++++++++
 setup.c                                | 13 ++++++
 5 files changed, 123 insertions(+)

diff --git a/Documentation/git-prune.txt b/Documentation/git-prune.txt
index 7a493c8..50e39ec 100644
--- a/Documentation/git-prune.txt
+++ b/Documentation/git-prune.txt
@@ -48,6 +48,9 @@ OPTIONS
 --expire <time>::
 	Only expire loose objects older than <time>.
 
+--repos::
+	Prune directories in $GIT_DIR/repos.
+
 <head>...::
 	In addition to objects
 	reachable from any of our references, keep objects
diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
index 543d874..bed4f1a 100644
--- a/Documentation/gitrepository-layout.txt
+++ b/Documentation/gitrepository-layout.txt
@@ -256,6 +256,25 @@ repos::
 	$GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/repos" will be
 	used instead.
 
+repos/<id>/gitdir::
+	A text file containing the absolute path back to the .git file
+	that points to here. This is used to check if the linked
+	repository has been manually removed and there is no need to
+	keep this directory any more. mtime of this file should be
+	updated every time the linked repository is accessed.
+
+repos/<id>/locked::
+	If this file exists, the linked repository may be on a
+	portable device and not available. It does not mean that the
+	linked repository is gone and `repos/<id>` could be
+	removed. The file's content contains a reason string on why
+	the repository is locked.
+
+repos/<id>/link::
+	If this file exists, it is a hard link to the linked .git
+	file. It is used to detect if the linked repository is
+	manually removed.
+
 SEE ALSO
 --------
 linkgit:git-init[1],
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 069e803..98a2f5f 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -898,12 +898,22 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	junk_git_dir = sb_repo.buf;
 	is_junk = 1;
 
+	/*
+	 * lock the incomplete repo so prune won't delete it, unlock
+	 * after the preparation is over.
+	 */
+	strbuf_addf(&sb, "%s/locked", sb_repo.buf);
+	write_file(sb.buf, 1, "initializing\n");
+
 	strbuf_addf(&sb_git, "%s/.git", path);
 	if (safe_create_leading_directories_const(sb_git.buf))
 		die_errno(_("could not create leading directories of '%s'"),
 			  sb_git.buf);
 	junk_work_tree = path;
 
+	strbuf_reset(&sb);
+	strbuf_addf(&sb, "%s/gitdir", sb_repo.buf);
+	write_file(sb.buf, 1, "%s\n", real_path(sb_git.buf));
 	write_file(sb_git.buf, 1, "gitdir: %s/repos/%s\n",
 		   real_path(get_git_common_dir()), name);
 	/*
@@ -912,6 +922,7 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	 * value would do because this value will be ignored and
 	 * replaced at the next (real) checkout.
 	 */
+	strbuf_reset(&sb);
 	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
 	write_file(sb.buf, 1, "%s\n", sha1_to_hex(new->commit->object.sha1));
 	strbuf_reset(&sb);
@@ -930,6 +941,9 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	ret = run_command(&cp);
 	if (!ret)
 		is_junk = 0;
+	strbuf_reset(&sb);
+	strbuf_addf(&sb, "%s/locked", sb_repo.buf);
+	unlink_or_warn(sb.buf);
 	strbuf_release(&sb);
 	strbuf_release(&sb_repo);
 	strbuf_release(&sb_git);
diff --git a/builtin/prune.c b/builtin/prune.c
index 144a3bd..6db6bcc 100644
--- a/builtin/prune.c
+++ b/builtin/prune.c
@@ -112,6 +112,70 @@ static void prune_object_dir(const char *path)
 	}
 }
 
+static const char *prune_repo_dir(const char *id, struct stat *st)
+{
+	char *path;
+	int fd, len;
+	if (file_exists(git_path("repos/%s/locked", id)))
+		return NULL;
+	if (stat(git_path("repos/%s/gitdir", id), st)) {
+		st->st_mtime = expire;
+		return _("gitdir does not exist");
+	}
+	fd = open(git_path("repos/%s/gitdir", id), O_RDONLY);
+	len = st->st_size;
+	path = xmalloc(len + 1);
+	read_in_full(fd, path, len);
+	close(fd);
+	while (path[len - 1] == '\n' || path[len - 1] == '\r')
+		len--;
+	path[len] = '\0';
+	if (!file_exists(path)) {
+		struct stat st_link;
+		free(path);
+		/*
+		 * the repo is moved manually and has not been
+		 * accessed since?
+		 */
+		if (!stat(git_path("repos/%s/link", id), &st_link) &&
+		    st_link.st_nlink > 1)
+			return NULL;
+		return _("gitdir points to non-existing file");
+	}
+	free(path);
+	return NULL;
+}
+
+static void prune_repos_dir(void)
+{
+	const char *reason;
+	DIR *dir = opendir(git_path("repos"));
+	struct dirent *d;
+	int removed = 0;
+	struct stat st;
+	if (!dir)
+		return;
+	while ((d = readdir(dir)) != NULL) {
+		if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
+			continue;
+		if ((reason = prune_repo_dir(d->d_name, &st)) != NULL &&
+		    st.st_mtime <= expire) {
+			struct strbuf sb = STRBUF_INIT;
+			if (show_only || verbose)
+				printf(_("Removing repos/%s: %s\n"), d->d_name, reason);
+			if (show_only)
+				continue;
+			strbuf_addstr(&sb, git_path("repos/%s", d->d_name));
+			remove_dir_recursively(&sb, 0);
+			strbuf_release(&sb);
+			removed = 1;
+		}
+	}
+	closedir(dir);
+	if (removed)
+		rmdir(git_path("repos"));
+}
+
 /*
  * Write errors (particularly out of space) can result in
  * failed temporary packs (and more rarely indexes and other
@@ -138,10 +202,12 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
 {
 	struct rev_info revs;
 	struct progress *progress = NULL;
+	int prune_repos = 0;
 	const struct option options[] = {
 		OPT__DRY_RUN(&show_only, N_("do not remove, show only")),
 		OPT__VERBOSE(&verbose, N_("report pruned objects")),
 		OPT_BOOL(0, "progress", &show_progress, N_("show progress")),
+		OPT_BOOL(0, "repos", &prune_repos, N_("prune .git/repos/")),
 		OPT_EXPIRY_DATE(0, "expire", &expire,
 				N_("expire objects older than <time>")),
 		OPT_END()
@@ -154,6 +220,14 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
 	init_revisions(&revs, prefix);
 
 	argc = parse_options(argc, argv, prefix, options, prune_usage, 0);
+
+	if (prune_repos) {
+		if (argc)
+			die(_("--repos does not take extra arguments"));
+		prune_repos_dir();
+		return 0;
+	}
+
 	while (argc--) {
 		unsigned char sha1[20];
 		const char *name = *argv++;
diff --git a/setup.c b/setup.c
index 8f90bc3..da2d669 100644
--- a/setup.c
+++ b/setup.c
@@ -390,6 +390,17 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 	return ret;
 }
 
+static void update_linked_gitdir(const char *gitfile, const char *gitdir)
+{
+	struct strbuf path = STRBUF_INIT;
+	struct stat st;
+
+	strbuf_addf(&path, "%s/gitfile", gitdir);
+	if (stat(path.buf, &st) || st.st_mtime + 24 * 3600 < time(NULL))
+		write_file(path.buf, 0, "%s\n", gitfile);
+	strbuf_release(&path);
+}
+
 /*
  * Try to read the location of the git directory from the .git file,
  * return path to git directory if found.
@@ -438,6 +449,8 @@ const char *read_gitfile(const char *path)
 
 	if (!is_git_directory(dir))
 		die("Not a git repository: %s", dir);
+
+	update_linked_gitdir(path, dir);
 	path = real_path(dir);
 
 	free(buf);
-- 
1.9.1.346.ga2b5940

[PATCH v6 28/32] gc: style change -- no SP before closing bracket

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/gc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index 8d219d8..53f1302 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -285,7 +285,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 		OPT__QUIET(&quiet, N_("suppress progress reporting")),
 		{ OPTION_STRING, 0, "prune", &prune_expire, N_("date"),
 			N_("prune unreferenced objects"),
-			PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire },
+			PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire},
 		OPT_BOOL(0, "aggressive", &aggressive, N_("be more thorough (increased runtime)")),
 		OPT_BOOL(0, "auto", &auto_gc, N_("enable auto-gc mode")),
 		OPT_BOOL(0, "force", &force, N_("force running gc even if there may be another gc running")),
@@ -298,7 +298,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 	argv_array_pushl(&pack_refs_cmd, "pack-refs", "--all", "--prune", NULL);
 	argv_array_pushl(&reflog, "reflog", "expire", "--all", NULL);
 	argv_array_pushl(&repack, "repack", "-d", "-l", NULL);
-	argv_array_pushl(&prune, "prune", "--expire", NULL );
+	argv_array_pushl(&prune, "prune", "--expire", NULL);
 	argv_array_pushl(&rerere, "rerere", "gc", NULL);
 
 	git_config(gc_config, NULL);
-- 
1.9.1.346.ga2b5940

[PATCH v6 29/32] gc: support prune --repos

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/config.txt |  7 +++++++
 builtin/gc.c             | 17 +++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 286e539..470f979 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1211,6 +1211,13 @@ gc.pruneexpire::
 	"now" may be used to disable this  grace period and always prune
 	unreachable objects immediately.
 
+gc.prunereposexpire::
+	When 'git gc' is run, it will call
+	'prune --repos --expire 3.months.ago'.
+	Override the grace period with this config variable. The value
+	"now" may be used to disable the grace period and always prune
+	$GIT_DIR/repos immediately.
+
 gc.reflogexpire::
 gc.<pattern>.reflogexpire::
 	'git reflog expire' removes reflog entries older than
diff --git a/builtin/gc.c b/builtin/gc.c
index 53f1302..1190183 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -33,11 +33,13 @@ static int gc_auto_threshold = 6700;
 static int gc_auto_pack_limit = 50;
 static int detach_auto = 1;
 static const char *prune_expire = "2.weeks.ago";
+static const char *prune_repos_expire = "3.months.ago";
 
 static struct argv_array pack_refs_cmd = ARGV_ARRAY_INIT;
 static struct argv_array reflog = ARGV_ARRAY_INIT;
 static struct argv_array repack = ARGV_ARRAY_INIT;
 static struct argv_array prune = ARGV_ARRAY_INIT;
+static struct argv_array prune_repos = ARGV_ARRAY_INIT;
 static struct argv_array rerere = ARGV_ARRAY_INIT;
 
 static char *pidfile;
@@ -92,6 +94,14 @@ static int gc_config(const char *var, const char *value, void *cb)
 		}
 		return git_config_string(&prune_expire, var, value);
 	}
+	if (!strcmp(var, "gc.prunereposexpire")) {
+		if (value && strcmp(value, "now")) {
+			unsigned long now = approxidate("now");
+			if (approxidate(value) >= now)
+				return error(_("Invalid %s: '%s'"), var, value);
+		}
+		return git_config_string(&prune_repos_expire, var, value);
+	}
 	return git_default_config(var, value, cb);
 }
 
@@ -299,6 +309,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 	argv_array_pushl(&reflog, "reflog", "expire", "--all", NULL);
 	argv_array_pushl(&repack, "repack", "-d", "-l", NULL);
 	argv_array_pushl(&prune, "prune", "--expire", NULL);
+	argv_array_pushl(&prune_repos, "prune", "--repos", "--expire", NULL);
 	argv_array_pushl(&rerere, "rerere", "gc", NULL);
 
 	git_config(gc_config, NULL);
@@ -368,6 +379,12 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 			return error(FAILED_RUN, prune.argv[0]);
 	}
 
+	if (prune_repos_expire) {
+		argv_array_push(&prune_repos, prune_repos_expire);
+		if (run_command_v_opt(prune_repos.argv, RUN_GIT_CMD))
+			return error(FAILED_RUN, prune_repos.argv[0]);
+	}
+
 	if (run_command_v_opt(rerere.argv, RUN_GIT_CMD))
 		return error(FAILED_RUN, rerere.argv[0]);
 
-- 
1.9.1.346.ga2b5940

[PATCH v6 30/32] count-objects: report unused files in $GIT_DIR/repos/...

[Nguyễn Thái Ngọc Duy]

In linked checkouts, borrowed parts like config is taken from
$GIT_COMMON_DIR. $GIT_DIR/config is never used. Report them as
garbage.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/count-objects.c |  4 +++-
 cache.h                 |  1 +
 path.c                  | 29 +++++++++++++++++++++++++++--
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/builtin/count-objects.c b/builtin/count-objects.c
index a7f70cb..d3a1620 100644
--- a/builtin/count-objects.c
+++ b/builtin/count-objects.c
@@ -102,8 +102,10 @@ int cmd_count_objects(int argc, const char **argv, const char *prefix)
 	/* we do not take arguments other than flags for now */
 	if (argc)
 		usage_with_options(count_objects_usage, opts);
-	if (verbose)
+	if (verbose) {
 		report_garbage = real_report_garbage;
+		report_linked_checkout_garbage();
+	}
 	memcpy(path, objdir, len);
 	if (len && objdir[len-1] != '/')
 		path[len++] = '/';
diff --git a/cache.h b/cache.h
index b363c00..39cf3f0 100644
--- a/cache.h
+++ b/cache.h
@@ -690,6 +690,7 @@ extern const char *mkpath(const char *fmt, ...) __attribute__((format (printf, 1
 extern const char *git_path(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
 extern const char *git_path_submodule(const char *path, const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
+extern void report_linked_checkout_garbage(void);
 
 /*
  * Return the name of the file in the local object database that would
diff --git a/path.c b/path.c
index e41d6b3..b5af137 100644
--- a/path.c
+++ b/path.c
@@ -4,6 +4,7 @@
 #include "cache.h"
 #include "strbuf.h"
 #include "string-list.h"
+#include "dir.h"
 
 static int get_st_mode_bits(const char *path, int *mode)
 {
@@ -91,9 +92,9 @@ static void replace_dir(struct strbuf *buf, int len, const char *newdir)
 }
 
 static const char *common_list[] = {
-	"/branches", "/hooks", "/info", "/logs", "/lost-found", "/modules",
+	"/branches", "/hooks", "/info", "!/logs", "/lost-found", "/modules",
 	"/objects", "/refs", "/remotes", "/repos", "/rr-cache", "/svn",
-	"config", "gc.pid", "packed-refs", "shallow",
+	"config", "!gc.pid", "packed-refs", "shallow",
 	NULL
 };
 
@@ -107,6 +108,8 @@ static void update_common_dir(struct strbuf *buf, int git_dir_len)
 	for (p = common_list; *p; p++) {
 		const char *path = *p;
 		int is_dir = 0;
+		if (*path == '!')
+			path++;
 		if (*path == '/') {
 			path++;
 			is_dir = 1;
@@ -122,6 +125,28 @@ static void update_common_dir(struct strbuf *buf, int git_dir_len)
 	}
 }
 
+void report_linked_checkout_garbage(void)
+{
+	struct strbuf sb = STRBUF_INIT;
+	const char **p;
+	int len;
+
+	if (!git_common_dir_env)
+		return;
+	strbuf_addf(&sb, "%s/", get_git_dir());
+	len = sb.len;
+	for (p = common_list; *p; p++) {
+		const char *path = *p;
+		if (*path == '!')
+			continue;
+		strbuf_setlen(&sb, len);
+		strbuf_addstr(&sb, path);
+		if (file_exists(sb.buf))
+			report_garbage("unused in linked checkout", sb.buf);
+	}
+	strbuf_release(&sb);
+}
+
 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 {
 	const char *base = buf->buf + git_dir_len;
-- 
1.9.1.346.ga2b5940

[PATCH v6 31/32] git_path(): keep "info/sparse-checkout" per work-tree

[Nguyễn Thái Ngọc Duy]

Currently git_path("info/sparse-checkout") resolves to
$GIT_COMMON_DIR/info/sparse-checkout in multiple worktree mode. It
makes more sense for the sparse checkout patterns to be per worktree,
so you can have multiple checkouts with different parts of the tree.

With this, "git checkout --to <new>" on a sparse checkout will create
<new> as a full checkout. Which is expected, it's how a new checkout
is made. The user can reshape the worktree afterwards.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 path.c                | 3 ++-
 t/t0060-path-utils.sh | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/path.c b/path.c
index b5af137..b1dd2bc 100644
--- a/path.c
+++ b/path.c
@@ -103,7 +103,8 @@ static void update_common_dir(struct strbuf *buf, int git_dir_len)
 	char *base = buf->buf + git_dir_len;
 	const char **p;
 
-	if (is_dir_file(base, "logs", "HEAD"))
+	if (is_dir_file(base, "logs", "HEAD") ||
+	    is_dir_file(base, "info", "sparse-checkout"))
 		return;	/* keep this in $GIT_DIR */
 	for (p = common_list; *p; p++) {
 		const char *path = *p;
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 2dabcef..da82aab 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -269,6 +269,7 @@ test_git_path GIT_COMMON_DIR=bar logs/HEAD                .git/logs/HEAD
 test_git_path GIT_COMMON_DIR=bar objects                  bar/objects
 test_git_path GIT_COMMON_DIR=bar objects/bar              bar/objects/bar
 test_git_path GIT_COMMON_DIR=bar info/exclude             bar/info/exclude
+test_git_path GIT_COMMON_DIR=bar info/sparse-checkout     .git/info/sparse-checkout
 test_git_path GIT_COMMON_DIR=bar remotes/bar              bar/remotes/bar
 test_git_path GIT_COMMON_DIR=bar branches/bar             bar/branches/bar
 test_git_path GIT_COMMON_DIR=bar logs/refs/heads/master   bar/logs/refs/heads/master
-- 
1.9.1.346.ga2b5940

[PATCH v6 32/32] checkout: don't require a work tree when checking out into a new one

[Nguyễn Thái Ngọc Duy]

From: Dennis Kaarsemaker <dennis@kaarsemaker.net>

For normal use cases, it does not make sense for 'checkout' to work on
a bare repository, without a worktree. But "checkout --to" is an
exception because it _creates_ a new worktree. Allow this option to
run on bare repositories.

People who check out from a bare repository should remember that
core.logallrefupdates is off by default and it should be turned back
on. `--to` cannot do this automatically behind the user's back because
some user may deliberately want no reflog.

For people interested in repository setup/discovery code,
is_bare_repository_cfg (aka "core.bare") is unchanged by this patch,
which means 'true' by default for bare repos. Fortunately when we get
the repo through a linked checkout, is_bare_repository_cfg is never
used. So all is still good.

[nd: commit message]

Signed-off-by: Dennis Kaarsemaker <dennis@kaarsemaker.net>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/checkout.c     |  3 +++
 git.c                  |  2 +-
 t/t2025-checkout-to.sh | 15 +++++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 98a2f5f..fd89d93 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1353,6 +1353,9 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	if (opts.new_worktree_mode)
 		opts.new_worktree = NULL;
 
+	if (!opts.new_worktree)
+		setup_work_tree();
+
 	if (conflict_style) {
 		opts.merge = 1; /* implied */
 		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
diff --git a/git.c b/git.c
index d6b4a55..04d6c88 100644
--- a/git.c
+++ b/git.c
@@ -384,7 +384,7 @@ static struct cmd_struct commands[] = {
 	{ "check-ignore", cmd_check_ignore, RUN_SETUP | NEED_WORK_TREE },
 	{ "check-mailmap", cmd_check_mailmap, RUN_SETUP },
 	{ "check-ref-format", cmd_check_ref_format },
-	{ "checkout", cmd_checkout, RUN_SETUP | NEED_WORK_TREE },
+	{ "checkout", cmd_checkout, RUN_SETUP },
 	{ "checkout-index", cmd_checkout_index,
 		RUN_SETUP | NEED_WORK_TREE},
 	{ "cherry", cmd_cherry, RUN_SETUP },
diff --git a/t/t2025-checkout-to.sh b/t/t2025-checkout-to.sh
index 2d35a9b..a219851 100755
--- a/t/t2025-checkout-to.sh
+++ b/t/t2025-checkout-to.sh
@@ -54,4 +54,19 @@ test_expect_success 'detach if the same branch is already checked out' '
 	)
 '
 
+test_expect_success 'checkout --to from a bare repo' '
+	(
+		git clone --bare . bare &&
+		cd bare &&
+		git checkout --to ../there2 master
+	)
+'
+
+test_expect_success 'checkout from a bare repo without --to' '
+	(
+		cd bare &&
+		test_must_fail git checkout master
+	)
+'
+
 test_done
-- 
1.9.1.346.ga2b5940

Re: [PATCH v6 28/32] gc: style change -- no SP before closing bracket

[Eric Sunshine]

On Wed, Jul 9, 2014 at 3:33 AM, Nguyễn Thái Ngọc Duy <pclouds@gmail.com> wrote:
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  builtin/gc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/gc.c b/builtin/gc.c
> index 8d219d8..53f1302 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -285,7 +285,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
>                 OPT__QUIET(&quiet, N_("suppress progress reporting")),
>                 { OPTION_STRING, 0, "prune", &prune_expire, N_("date"),
>                         N_("prune unreferenced objects"),
> -                       PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire },
> +                       PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire},

Yet, there is a space after the opening '{'. So, this is now
inconsistently formatted as:

    { foo, bar}

>                 OPT_BOOL(0, "aggressive", &aggressive, N_("be more thorough (increased runtime)")),
>                 OPT_BOOL(0, "auto", &auto_gc, N_("enable auto-gc mode")),
>                 OPT_BOOL(0, "force", &force, N_("force running gc even if there may be another gc running")),
> @@ -298,7 +298,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
>         argv_array_pushl(&pack_refs_cmd, "pack-refs", "--all", "--prune", NULL);
>         argv_array_pushl(&reflog, "reflog", "expire", "--all", NULL);
>         argv_array_pushl(&repack, "repack", "-d", "-l", NULL);
> -       argv_array_pushl(&prune, "prune", "--expire", NULL );
> +       argv_array_pushl(&prune, "prune", "--expire", NULL);
>         argv_array_pushl(&rerere, "rerere", "gc", NULL);
>
>         git_config(gc_config, NULL);
> --
> 1.9.1.346.ga2b5940

Re: [PATCH v6 29/32] gc: support prune --repos

[Eric Sunshine]

On Wed, Jul 9, 2014 at 3:33 AM, Nguyễn Thái Ngọc Duy <pclouds@gmail.com> wrote:
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  Documentation/config.txt |  7 +++++++
>  builtin/gc.c             | 17 +++++++++++++++++
>  2 files changed, 24 insertions(+)
>
> diff --git a/Documentation/config.txt b/Documentation/config.txt
> index 286e539..470f979 100644
> --- a/Documentation/config.txt
> +++ b/Documentation/config.txt
> @@ -1211,6 +1211,13 @@ gc.pruneexpire::
>         "now" may be used to disable this  grace period and always prune
>         unreachable objects immediately.
>
> +gc.prunereposexpire::
> +       When 'git gc' is run, it will call
> +       'prune --repos --expire 3.months.ago'.
> +       Override the grace period with this config variable. The value
> +       "now" may be used to disable the grace period and always prune
> +       $GIT_DIR/repos immediately.

nit: This reads very slightly better without "always":

    ... disable the grace period and prune [...] immediately.

More below.

> +
>  gc.reflogexpire::
>  gc.<pattern>.reflogexpire::
>         'git reflog expire' removes reflog entries older than
> diff --git a/builtin/gc.c b/builtin/gc.c
> index 53f1302..1190183 100644
> --- a/builtin/gc.c
> +++ b/builtin/gc.c
> @@ -33,11 +33,13 @@ static int gc_auto_threshold = 6700;
>  static int gc_auto_pack_limit = 50;
>  static int detach_auto = 1;
>  static const char *prune_expire = "2.weeks.ago";
> +static const char *prune_repos_expire = "3.months.ago";
>
>  static struct argv_array pack_refs_cmd = ARGV_ARRAY_INIT;
>  static struct argv_array reflog = ARGV_ARRAY_INIT;
>  static struct argv_array repack = ARGV_ARRAY_INIT;
>  static struct argv_array prune = ARGV_ARRAY_INIT;
> +static struct argv_array prune_repos = ARGV_ARRAY_INIT;
>  static struct argv_array rerere = ARGV_ARRAY_INIT;
>
>  static char *pidfile;
> @@ -92,6 +94,14 @@ static int gc_config(const char *var, const char *value, void *cb)
>                 }
>                 return git_config_string(&prune_expire, var, value);
>         }
> +       if (!strcmp(var, "gc.prunereposexpire")) {
> +               if (value && strcmp(value, "now")) {
> +                       unsigned long now = approxidate("now");
> +                       if (approxidate(value) >= now)
> +                               return error(_("Invalid %s: '%s'"), var, value);
> +               }
> +               return git_config_string(&prune_repos_expire, var, value);

This logic is copied from the "gc.pruneexpire" case immediately above
it. Would it make sense to factor it out into a helper function (or is
it not worth the bother for just two cases)?

> +       }
>         return git_default_config(var, value, cb);
>  }
>
> @@ -299,6 +309,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
>         argv_array_pushl(&reflog, "reflog", "expire", "--all", NULL);
>         argv_array_pushl(&repack, "repack", "-d", "-l", NULL);
>         argv_array_pushl(&prune, "prune", "--expire", NULL);
> +       argv_array_pushl(&prune_repos, "prune", "--repos", "--expire", NULL);
>         argv_array_pushl(&rerere, "rerere", "gc", NULL);
>
>         git_config(gc_config, NULL);
> @@ -368,6 +379,12 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
>                         return error(FAILED_RUN, prune.argv[0]);
>         }
>
> +       if (prune_repos_expire) {
> +               argv_array_push(&prune_repos, prune_repos_expire);
> +               if (run_command_v_opt(prune_repos.argv, RUN_GIT_CMD))
> +                       return error(FAILED_RUN, prune_repos.argv[0]);
> +       }
> +
>         if (run_command_v_opt(rerere.argv, RUN_GIT_CMD))
>                 return error(FAILED_RUN, rerere.argv[0]);
>
> --
> 1.9.1.346.ga2b5940

Re: [PATCH v6 27/32] prune: strategies for linked checkouts

[Eric Sunshine]

On Wed, Jul 9, 2014 at 3:33 AM, Nguyễn Thái Ngọc Duy <pclouds@gmail.com> wrote:
> (alias R=$GIT_COMMON_DIR/repos/<id>)
>
>  - linked checkouts are supposed to keep its location in $R/gitdir up
>    to date. The use case is auto fixup after a manual checkout move.
>
>  - linked checkouts are supposed to update mtime of $R/gitdir. If
>    $R/gitdir's mtime is older than a limit, and it points to nowhere,
>    repos/<id> is to be pruned.
>
>  - If $R/locked exists, repos/<id> is not supposed to be pruned. If
>    $R/locked exists and $R/gitdir's mtime is older than a really long
>    limit, warn about old unused repo.
>
>  - "git checkout --to" is supposed to make a hard link named $R/link
>    pointing to the .git file on supported file systems to help detect
>    the user manually deleting the checkout. If $R/link exists and its
>    link count is greated than 1, the repo is kept.
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
> diff --git a/builtin/prune.c b/builtin/prune.c
> index 144a3bd..6db6bcc 100644
> --- a/builtin/prune.c
> +++ b/builtin/prune.c
> @@ -112,6 +112,70 @@ static void prune_object_dir(const char *path)
>         }
>  }
>
> +static const char *prune_repo_dir(const char *id, struct stat *st)
> +{
> +       char *path;
> +       int fd, len;
> +       if (file_exists(git_path("repos/%s/locked", id)))
> +               return NULL;
> +       if (stat(git_path("repos/%s/gitdir", id), st)) {
> +               st->st_mtime = expire;
> +               return _("gitdir does not exist");

If a plain file exists in 'repos' for some reason, it will be caught
by this case. Would it make sense, however, to handle that specially
and report a more accurate message, such as "not a repo" or some such?

> +       }
> +       fd = open(git_path("repos/%s/gitdir", id), O_RDONLY);

If 'gitdir' fails to open for some reason (lack of permissions, it's a
directory, etc.), the subsequent read_in_full() will crash.

> +       len = st->st_size;
> +       path = xmalloc(len + 1);
> +       read_in_full(fd, path, len);
> +       close(fd);

strbuf_readfile() might make this a bit cleaner (though has higher overhead).

> +       while (path[len - 1] == '\n' || path[len - 1] == '\r')
> +               len--;

If, for some reason, 'gitdir' content is empty or consists only of CR
and LF, this will access memory outside of the allocated region.
Probably want:

    while (len > 0 && (... || ...))

> +       path[len] = '\0';
> +       if (!file_exists(path)) {

What happens if 'path' ends up empty (due to hand-editing of 'gitdir'
by the user, for instance)? Does this case deserve an appropriate
diagnostic ("corrupt 'gitdir' file" or something)?

> +               struct stat st_link;
> +               free(path);
> +               /*
> +                * the repo is moved manually and has not been
> +                * accessed since?
> +                */
> +               if (!stat(git_path("repos/%s/link", id), &st_link) &&
> +                   st_link.st_nlink > 1)
> +                       return NULL;
> +               return _("gitdir points to non-existing file");

s/existing/existent/
s/file/location/

> +       }
> +       free(path);
> +       return NULL;
> +}
> +
> +static void prune_repos_dir(void)
> +{
> +       const char *reason;
> +       DIR *dir = opendir(git_path("repos"));
> +       struct dirent *d;
> +       int removed = 0;
> +       struct stat st;
> +       if (!dir)
> +               return;
> +       while ((d = readdir(dir)) != NULL) {
> +               if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
> +                       continue;
> +               if ((reason = prune_repo_dir(d->d_name, &st)) != NULL &&
> +                   st.st_mtime <= expire) {
> +                       struct strbuf sb = STRBUF_INIT;
> +                       if (show_only || verbose)
> +                               printf(_("Removing repos/%s: %s\n"), d->d_name, reason);
> +                       if (show_only)
> +                               continue;
> +                       strbuf_addstr(&sb, git_path("repos/%s", d->d_name));
> +                       remove_dir_recursively(&sb, 0);

What happens if this entry in 'repos' is a plain file (or other
non-directory)? Based upon my reading of remove_dir_recursively(), it
won't be deleted, yet the logic of prune_repo_dir() implies that such
an entry should be pruned. Perhaps handle this case specially with
unlink()?

> +                       strbuf_release(&sb);
> +                       removed = 1;
> +               }
> +       }
> +       closedir(dir);
> +       if (removed)
> +               rmdir(git_path("repos"));

This works, but at first glance it seems strange not to be checking
'show_only' before calling destructive rmdir().

However, stepping back, it's not quite clear what the intent is.
Ignoring the return value of rmdir() implies that you trust it to Do
The Right Thing: succeed when 'repos' is empty and fail when not. This
assumption of behavior applies regardless of whether or not any
content of 'repos' was removed, so the 'removed' flag does not seem
beneficial.

Moreover, the 'removed' flag actively prevents the 'repos' directory
from being pruned in the corner case where the user manually emptied
the content of 'repos' before invoking "git prune". Therefore, it
might be simpler to drop the 'removed' variable altogether and
rephrase as:

    if (!show_only)
        rmdir(git_path("repos"));

> +}
> +
>  /*
>   * Write errors (particularly out of space) can result in
>   * failed temporary packs (and more rarely indexes and other
> @@ -138,10 +202,12 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
>  {
>         struct rev_info revs;
>         struct progress *progress = NULL;
> +       int prune_repos = 0;
>         const struct option options[] = {
>                 OPT__DRY_RUN(&show_only, N_("do not remove, show only")),
>                 OPT__VERBOSE(&verbose, N_("report pruned objects")),
>                 OPT_BOOL(0, "progress", &show_progress, N_("show progress")),
> +               OPT_BOOL(0, "repos", &prune_repos, N_("prune .git/repos/")),
>                 OPT_EXPIRY_DATE(0, "expire", &expire,
>                                 N_("expire objects older than <time>")),
>                 OPT_END()
> @@ -154,6 +220,14 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
>         init_revisions(&revs, prefix);
>
>         argc = parse_options(argc, argv, prefix, options, prune_usage, 0);
> +
> +       if (prune_repos) {
> +               if (argc)
> +                       die(_("--repos does not take extra arguments"));
> +               prune_repos_dir();
> +               return 0;
> +       }
> +
>         while (argc--) {
>                 unsigned char sha1[20];
>                 const char *name = *argv++;
> diff --git a/setup.c b/setup.c
> index 8f90bc3..da2d669 100644
> --- a/setup.c
> +++ b/setup.c
> @@ -390,6 +390,17 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
>         return ret;
>  }
>
> +static void update_linked_gitdir(const char *gitfile, const char *gitdir)
> +{
> +       struct strbuf path = STRBUF_INIT;
> +       struct stat st;
> +
> +       strbuf_addf(&path, "%s/gitfile", gitdir);
> +       if (stat(path.buf, &st) || st.st_mtime + 24 * 3600 < time(NULL))
> +               write_file(path.buf, 0, "%s\n", gitfile);
> +       strbuf_release(&path);
> +}
> +
>  /*
>   * Try to read the location of the git directory from the .git file,
>   * return path to git directory if found.
> @@ -438,6 +449,8 @@ const char *read_gitfile(const char *path)
>
>         if (!is_git_directory(dir))
>                 die("Not a git repository: %s", dir);
> +
> +       update_linked_gitdir(path, dir);
>         path = real_path(dir);
>
>         free(buf);
> --
> 1.9.1.346.ga2b5940

Re: [PATCH v6 00/32] Support multiple checkouts

[Dennis Kaarsemaker]

Tested-by: Dennis Kaarsemaker <dennis@kaarsemaker.net>

I've been using this branch for a little while now and have no breakages
to report. Max Kirillov reported some bugs in the interaction with
submodules which I plan to chase when I have some time unless someone
beats me to it :)

On wo, 2014-07-09 at 14:32 +0700, Nguyễn Thái Ngọc Duy wrote:
> This is basically a reroll from what was parked on 'pu' with two
> new patches at the end: one to not share info/sparse-checkout
> across worktrees, and one to allow 'checkout --to` from a bare
> repository.
> 
> I cherry-picked two patches from jk/xstrfmt (on next) because they
> result in non-trivial conflicts. When this series is merged with
> jk/xstrfmt, you still get conflicts in environment.c, but you can just
> pick up my changes and drop Jeff's.
> 
> Dennis Kaarsemaker (1):
>   checkout: don't require a work tree when checking out into a new one
> 
> Jeff King (2):
>   setup_git_env: use git_pathdup instead of xmalloc + sprintf
>   setup_git_env(): introduce git_path_from_env() helper
> 
> Nguyễn Thái Ngọc Duy (29):
>   path.c: make get_pathname() return strbuf instead of static buffer
>   path.c: make get_pathname() call sites return const char *
>   git_snpath(): retire and replace with strbuf_git_path()
>   path.c: rename vsnpath() to do_git_path()
>   path.c: group git_path(), git_pathdup() and strbuf_git_path() together
>   git_path(): be aware of file relocation in $GIT_DIR
>   *.sh: respect $GIT_INDEX_FILE
>   reflog: avoid constructing .lock path with git_path
>   fast-import: use git_path() for accessing .git dir instead of get_git_dir()
>   commit: use SEQ_DIR instead of hardcoding "sequencer"
>   $GIT_COMMON_DIR: a new environment variable
>   git-sh-setup.sh: use rev-parse --git-path to get $GIT_DIR/objects
>   *.sh: avoid hardcoding $GIT_DIR/hooks/...
>   git-stash: avoid hardcoding $GIT_DIR/logs/....
>   setup.c: convert is_git_directory() to use strbuf
>   setup.c: detect $GIT_COMMON_DIR in is_git_directory()
>   setup.c: convert check_repository_format_gently to use strbuf
>   setup.c: detect $GIT_COMMON_DIR check_repository_format_gently()
>   setup.c: support multi-checkout repo setup
>   wrapper.c: wrapper to open a file, fprintf then close
>   use new wrapper write_file() for simple file writing
>   checkout: support checking out into a new working directory
>   checkout: clean up half-prepared directories in --to mode
>   checkout: detach if the branch is already checked out elsewhere
>   prune: strategies for linked checkouts
>   gc: style change -- no SP before closing bracket
>   gc: support prune --repos
>   count-objects: report unused files in $GIT_DIR/repos/...
>   git_path(): keep "info/sparse-checkout" per work-tree
> 
>  Documentation/config.txt               |   9 ++
>  Documentation/git-checkout.txt         |  34 +++++
>  Documentation/git-prune.txt            |   3 +
>  Documentation/git-rev-parse.txt        |  10 ++
>  Documentation/git.txt                  |   9 ++
>  Documentation/gitrepository-layout.txt |  75 ++++++++--
>  builtin/branch.c                       |   4 +-
>  builtin/checkout.c                     | 248 ++++++++++++++++++++++++++++++++-
>  builtin/clone.c                        |   9 +-
>  builtin/commit.c                       |   2 +-
>  builtin/count-objects.c                |   4 +-
>  builtin/fetch.c                        |   5 +-
>  builtin/fsck.c                         |   4 +-
>  builtin/gc.c                           |  21 ++-
>  builtin/init-db.c                      |   7 +-
>  builtin/prune.c                        |  74 ++++++++++
>  builtin/receive-pack.c                 |   2 +-
>  builtin/reflog.c                       |   2 +-
>  builtin/remote.c                       |   2 +-
>  builtin/repack.c                       |   8 +-
>  builtin/rev-parse.c                    |  11 ++
>  cache.h                                |  17 ++-
>  daemon.c                               |  11 +-
>  environment.c                          |  45 ++++--
>  fast-import.c                          |   7 +-
>  git-am.sh                              |  22 +--
>  git-pull.sh                            |   2 +-
>  git-rebase--interactive.sh             |   6 +-
>  git-rebase--merge.sh                   |   6 +-
>  git-rebase.sh                          |   4 +-
>  git-sh-setup.sh                        |   2 +-
>  git-stash.sh                           |   6 +-
>  git.c                                  |   2 +-
>  notes-merge.c                          |   6 +-
>  path.c                                 | 234 +++++++++++++++++++++----------
>  refs.c                                 |  86 +++++++-----
>  refs.h                                 |   2 +-
>  run-command.c                          |   4 +-
>  run-command.h                          |   2 +-
>  setup.c                                | 124 +++++++++++++----
>  sha1_file.c                            |   2 +-
>  submodule.c                            |   9 +-
>  t/t0060-path-utils.sh                  |  35 +++++
>  t/t1501-worktree.sh                    |  76 ++++++++++
>  t/t1510-repo-setup.sh                  |   1 +
>  t/t2025-checkout-to.sh (new +x)        |  72 ++++++++++
>  templates/hooks--applypatch-msg.sample |   4 +-
>  templates/hooks--pre-applypatch.sample |   4 +-
>  trace.c                                |   1 +
>  transport.c                            |   8 +-
>  wrapper.c                              |  31 +++++
>  51 files changed, 1109 insertions(+), 265 deletions(-)
>  create mode 100755 t/t2025-checkout-to.sh
> 


-- 
Dennis Kaarsemaker
www.kaarsemaker.net

Re: [PATCH v6 26/32] checkout: detach if the branch is already checked out elsewhere

[Max Kirillov]

On Wed, Jul 09, 2014 at 02:33:11PM +0700, Nguyễn Thái Ngọc Duy wrote:
> +static int check_linked_checkout(struct branch_info *new,
> +				  const char *name, const char *path)
> +{
...
> +	if (!strncmp(start, new->path, end - start) &&
> +	    new->path[end - start] == '\0') {

This also detaches if the "holding checkout" is _this_
checkout, that is, when you are checking out the currently
checked our branch.

-- 
Max

[PATCH v7 00/31] Support multiple checkouts

[Nguyễn Thái Ngọc Duy]

v7 fixes all comments from Eric and Max. Jeff's two patches are
dropped because they have landed in latest master now. Diff against
v6:

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 470f979..57999fa 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1215,7 +1215,7 @@ gc.prunereposexpire::
 	When 'git gc' is run, it will call
 	'prune --repos --expire 3.months.ago'.
 	Override the grace period with this config variable. The value
-	"now" may be used to disable the grace period and always prune
+	"now" may be used to disable the grace period and prune
 	$GIT_DIR/repos immediately.
 
 gc.reflogexpire::
diff --git a/builtin/checkout.c b/builtin/checkout.c
index dc8503a..c83f476 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1010,15 +1010,13 @@ static int check_linked_checkout(struct branch_info *new,
 				  const char *name, const char *path)
 {
 	struct strbuf sb = STRBUF_INIT;
-	char *start, *end;
-	if (strbuf_read_file(&sb, path, 0) < 0)
-		return 0;
-	if (!starts_with(sb.buf, "ref:")) {
+	const char *start, *end;
+	if (strbuf_read_file(&sb, path, 0) < 0 ||
+	    !skip_prefix(sb.buf, "ref:", &start)) {
 		strbuf_release(&sb);
 		return 0;
 	}
 
-	start = sb.buf + 4;
 	while (isspace(*start))
 		start++;
 	end = start;
@@ -1200,8 +1198,14 @@ static int parse_branchname_arg(int argc, const char **argv,
 	else
 		new->path = NULL; /* not an existing branch */
 
-	if (new->path)
-		check_linked_checkouts(new);
+	if (new->path) {
+		unsigned char sha1[20];
+		int flag;
+		char *head_ref = resolve_refdup("HEAD", sha1, 0, &flag);
+		if (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path))
+			check_linked_checkouts(new);
+		free(head_ref);
+	}
 
 	new->commit = lookup_commit_reference_gently(rev, 1);
 	if (!new->commit) {
diff --git a/builtin/gc.c b/builtin/gc.c
index 1190183..0c65808 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -57,6 +57,17 @@ static void remove_pidfile_on_signal(int signo)
 	raise(signo);
 }
 
+static int git_config_date_string(const char **output,
+				  const char *var, const char *value)
+{
+	if (value && strcmp(value, "now")) {
+		unsigned long now = approxidate("now");
+		if (approxidate(value) >= now)
+			return error(_("Invalid %s: '%s'"), var, value);
+	}
+	return git_config_string(output, var, value);
+}
+
 static int gc_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "gc.packrefs")) {
@@ -86,22 +97,10 @@ static int gc_config(const char *var, const char *value, void *cb)
 		detach_auto = git_config_bool(var, value);
 		return 0;
 	}
-	if (!strcmp(var, "gc.pruneexpire")) {
-		if (value && strcmp(value, "now")) {
-			unsigned long now = approxidate("now");
-			if (approxidate(value) >= now)
-				return error(_("Invalid %s: '%s'"), var, value);
-		}
-		return git_config_string(&prune_expire, var, value);
-	}
-	if (!strcmp(var, "gc.prunereposexpire")) {
-		if (value && strcmp(value, "now")) {
-			unsigned long now = approxidate("now");
-			if (approxidate(value) >= now)
-				return error(_("Invalid %s: '%s'"), var, value);
-		}
-		return git_config_string(&prune_repos_expire, var, value);
-	}
+	if (!strcmp(var, "gc.pruneexpire"))
+		return git_config_date_string(&prune_expire, var, value);
+	if (!strcmp(var, "gc.prunereposexpire"))
+		return git_config_date_string(&prune_repos_expire, var, value);
 	return git_default_config(var, value, cb);
 }
 
@@ -295,7 +294,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 		OPT__QUIET(&quiet, N_("suppress progress reporting")),
 		{ OPTION_STRING, 0, "prune", &prune_expire, N_("date"),
 			N_("prune unreferenced objects"),
-			PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire},
+			PARSE_OPT_OPTARG, NULL, (intptr_t)prune_expire },
 		OPT_BOOL(0, "aggressive", &aggressive, N_("be more thorough (increased runtime)")),
 		OPT_BOOL(0, "auto", &auto_gc, N_("enable auto-gc mode")),
 		OPT_BOOL(0, "force", &force, N_("force running gc even if there may be another gc running")),
diff --git a/builtin/prune.c b/builtin/prune.c
index 6db6bcc..28b7adf 100644
--- a/builtin/prune.c
+++ b/builtin/prune.c
@@ -112,23 +112,41 @@ static void prune_object_dir(const char *path)
 	}
 }
 
-static const char *prune_repo_dir(const char *id, struct stat *st)
+static int prune_repo_dir(const char *id, struct stat *st, struct strbuf *reason)
 {
 	char *path;
 	int fd, len;
+
+	if (!is_directory(git_path("repos/%s", id))) {
+		strbuf_addf(reason, _("Removing repos/%s: not a valid directory"), id);
+		return 1;
+	}
 	if (file_exists(git_path("repos/%s/locked", id)))
-		return NULL;
+		return 0;
 	if (stat(git_path("repos/%s/gitdir", id), st)) {
 		st->st_mtime = expire;
-		return _("gitdir does not exist");
+		strbuf_addf(reason, _("Removing repos/%s: gitdir file does not exist"), id);
+		return 1;
 	}
 	fd = open(git_path("repos/%s/gitdir", id), O_RDONLY);
+	if (fd < 0) {
+		st->st_mtime = expire;
+		strbuf_addf(reason, _("Removing repos/%s: unable to read gitdir file (%s)"),
+			    id, strerror(errno));
+		return 1;
+	}
 	len = st->st_size;
 	path = xmalloc(len + 1);
 	read_in_full(fd, path, len);
 	close(fd);
-	while (path[len - 1] == '\n' || path[len - 1] == '\r')
+	while (len && (path[len - 1] == '\n' || path[len - 1] == '\r'))
 		len--;
+	if (!len) {
+		st->st_mtime = expire;
+		strbuf_addf(reason, _("Removing repos/%s: invalid gitdir file"), id);
+		free(path);
+		return 1;
+	}
 	path[len] = '\0';
 	if (!file_exists(path)) {
 		struct stat st_link;
@@ -139,41 +157,48 @@ static const char *prune_repo_dir(const char *id, struct stat *st)
 		 */
 		if (!stat(git_path("repos/%s/link", id), &st_link) &&
 		    st_link.st_nlink > 1)
-			return NULL;
-		return _("gitdir points to non-existing file");
+			return 0;
+		strbuf_addf(reason, _("Removing repos/%s: gitdir file points to non-existent location"), id);
+		return 1;
 	}
 	free(path);
-	return NULL;
+	return 0;
 }
 
 static void prune_repos_dir(void)
 {
-	const char *reason;
+	struct strbuf reason = STRBUF_INIT;
+	struct strbuf path = STRBUF_INIT;
 	DIR *dir = opendir(git_path("repos"));
 	struct dirent *d;
-	int removed = 0;
+	int ret;
 	struct stat st;
 	if (!dir)
 		return;
 	while ((d = readdir(dir)) != NULL) {
 		if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
 			continue;
-		if ((reason = prune_repo_dir(d->d_name, &st)) != NULL &&
-		    st.st_mtime <= expire) {
-			struct strbuf sb = STRBUF_INIT;
-			if (show_only || verbose)
-				printf(_("Removing repos/%s: %s\n"), d->d_name, reason);
-			if (show_only)
-				continue;
-			strbuf_addstr(&sb, git_path("repos/%s", d->d_name));
-			remove_dir_recursively(&sb, 0);
-			strbuf_release(&sb);
-			removed = 1;
-		}
+		strbuf_reset(&reason);
+		if (!prune_repo_dir(d->d_name, &st, &reason) ||
+		    st.st_mtime > expire)
+			continue;
+		if (show_only || verbose)
+			printf("%s\n", reason.buf);
+		if (show_only)
+			continue;
+		strbuf_reset(&path);
+		strbuf_addstr(&path, git_path("repos/%s", d->d_name));
+		ret = remove_dir_recursively(&path, 0);
+		if (ret < 0 && errno == ENOTDIR)
+			ret = unlink(path.buf);
+		if (ret)
+			error(_("failed to remove: %s"), strerror(errno));
 	}
 	closedir(dir);
-	if (removed)
+	if (!show_only)
 		rmdir(git_path("repos"));
+	strbuf_release(&reason);
+	strbuf_release(&path);
 }
 
 /*
diff --git a/t/t2025-checkout-to.sh b/t/t2025-checkout-to.sh
index a219851..b0d97a0 100755
--- a/t/t2025-checkout-to.sh
+++ b/t/t2025-checkout-to.sh
@@ -54,6 +54,14 @@ test_expect_success 'detach if the same branch is already checked out' '
 	)
 '
 
+test_expect_success 'not detach on re-checking out current branch' '
+	(
+		cd there &&
+		git checkout newmaster &&
+		git symbolic-ref HEAD
+	)
+'
+
 test_expect_success 'checkout --to from a bare repo' '
 	(
 		git clone --bare . bare &&
diff --git a/t/t2026-prune-linked-checkouts.sh b/t/t2026-prune-linked-checkouts.sh
new file mode 100755
index 0000000..4ccfa4e
--- /dev/null
+++ b/t/t2026-prune-linked-checkouts.sh
@@ -0,0 +1,84 @@
+#!/bin/sh
+
+test_description='prune $GIT_DIR/repos'
+
+. ./test-lib.sh
+
+test_expect_success 'prune --repos on normal repo' '
+	git prune --repos &&
+	test_must_fail git prune --repos abc
+'
+
+test_expect_success 'prune files inside $GIT_DIR/repos' '
+	mkdir .git/repos &&
+	: >.git/repos/abc &&
+	git prune --repos --verbose >actual &&
+	cat >expect <<EOF &&
+Removing repos/abc: not a valid directory
+EOF
+	test_i18ncmp expect actual &&
+	! test -f .git/repos/abc &&
+	! test -d .git/repos
+'
+
+test_expect_success 'prune directories without gitdir' '
+	mkdir -p .git/repos/def/abc &&
+	: >.git/repos/def/def &&
+	cat >expect <<EOF &&
+Removing repos/def: gitdir file does not exist
+EOF
+	git prune --repos --verbose >actual &&
+	test_i18ncmp expect actual &&
+	! test -d .git/repos/def &&
+	! test -d .git/repos
+'
+
+test_expect_success POSIXPERM 'prune directories with unreadable gitdir' '
+	mkdir -p .git/repos/def/abc &&
+	: >.git/repos/def/def &&
+	: >.git/repos/def/gitdir &&
+	chmod u-r .git/repos/def/gitdir &&
+	git prune --repos --verbose >actual &&
+	test_i18ngrep "Removing repos/def: unable to read gitdir file" actual &&
+	! test -d .git/repos/def &&
+	! test -d .git/repos
+'
+
+test_expect_success 'prune directories with invalid gitdir' '
+	mkdir -p .git/repos/def/abc &&
+	: >.git/repos/def/def &&
+	: >.git/repos/def/gitdir &&
+	git prune --repos --verbose >actual &&
+	test_i18ngrep "Removing repos/def: invalid gitdir file" actual &&
+	! test -d .git/repos/def &&
+	! test -d .git/repos
+'
+
+test_expect_success 'prune directories with gitdir pointing to nowhere' '
+	mkdir -p .git/repos/def/abc &&
+	: >.git/repos/def/def &&
+	echo "$TRASH_DIRECTORY"/nowhere >.git/repos/def/gitdir &&
+	git prune --repos --verbose >actual &&
+	test_i18ngrep "Removing repos/def: gitdir file points to non-existent location" actual &&
+	! test -d .git/repos/def &&
+	! test -d .git/repos
+'
+
+test_expect_success 'not prune locked checkout' '
+	test_when_finished rm -r .git/repos
+	mkdir -p .git/repos/ghi &&
+	: >.git/repos/ghi/locked &&
+	git prune --repos &&
+	test -d .git/repos/ghi
+'
+
+test_expect_success 'not prune recent checkouts' '
+	test_when_finished rm -r .git/repos
+	mkdir zz &&
+	mkdir -p .git/repos/jlm &&
+	echo "$TRASH_DIRECTORY"/zz >.git/repos/jlm/gitdir &&
+	git prune --repos --verbose &&
+	test -d .git/repos/jlm
+'
+
+test_done

-- 
1.9.1.346.ga2b5940

[PATCH v7 01/31] path.c: make get_pathname() return strbuf instead of static buffer

[Nguyễn Thái Ngọc Duy]

We've been avoiding PATH_MAX whenever possible. This patch makes
get_pathname() return a strbuf and updates the callers to take
advantage of this. The code is simplified as we no longer need to
worry about buffer overflow.

vsnpath() behavior is changed slightly: previously it always clears
the buffer before writing, now it just appends. Fortunately this is a
static function and all of its callers prepare the buffer properly:
git_path() gets the buffer from get_pathname() which resets the
buffer, the remaining call sites start with STRBUF_INIT'd buffer.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 path.c | 120 ++++++++++++++++++++++++++++-------------------------------------
 1 file changed, 51 insertions(+), 69 deletions(-)

diff --git a/path.c b/path.c
index bc804a3..42ef3af 100644
--- a/path.c
+++ b/path.c
@@ -16,11 +16,15 @@ static int get_st_mode_bits(const char *path, int *mode)
 
 static char bad_path[] = "/bad-path/";
 
-static char *get_pathname(void)
+static struct strbuf *get_pathname(void)
 {
-	static char pathname_array[4][PATH_MAX];
+	static struct strbuf pathname_array[4] = {
+		STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
+	};
 	static int index;
-	return pathname_array[3 & ++index];
+	struct strbuf *sb = &pathname_array[3 & ++index];
+	strbuf_reset(sb);
+	return sb;
 }
 
 static char *cleanup_path(char *path)
@@ -34,6 +38,13 @@ static char *cleanup_path(char *path)
 	return path;
 }
 
+static void strbuf_cleanup_path(struct strbuf *sb)
+{
+	char *path = cleanup_path(sb->buf);
+	if (path > sb->buf)
+		strbuf_remove(sb, 0, path - sb->buf);
+}
+
 char *mksnpath(char *buf, size_t n, const char *fmt, ...)
 {
 	va_list args;
@@ -49,85 +60,70 @@ char *mksnpath(char *buf, size_t n, const char *fmt, ...)
 	return cleanup_path(buf);
 }
 
-static char *vsnpath(char *buf, size_t n, const char *fmt, va_list args)
+static void vsnpath(struct strbuf *buf, const char *fmt, va_list args)
 {
 	const char *git_dir = get_git_dir();
-	size_t len;
-
-	len = strlen(git_dir);
-	if (n < len + 1)
-		goto bad;
-	memcpy(buf, git_dir, len);
-	if (len && !is_dir_sep(git_dir[len-1]))
-		buf[len++] = '/';
-	len += vsnprintf(buf + len, n - len, fmt, args);
-	if (len >= n)
-		goto bad;
-	return cleanup_path(buf);
-bad:
-	strlcpy(buf, bad_path, n);
-	return buf;
+	strbuf_addstr(buf, git_dir);
+	if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
+		strbuf_addch(buf, '/');
+	strbuf_vaddf(buf, fmt, args);
+	strbuf_cleanup_path(buf);
 }
 
 char *git_snpath(char *buf, size_t n, const char *fmt, ...)
 {
-	char *ret;
+	struct strbuf sb = STRBUF_INIT;
 	va_list args;
 	va_start(args, fmt);
-	ret = vsnpath(buf, n, fmt, args);
+	vsnpath(&sb, fmt, args);
 	va_end(args);
-	return ret;
+	if (sb.len >= n)
+		strlcpy(buf, bad_path, n);
+	else
+		memcpy(buf, sb.buf, sb.len + 1);
+	strbuf_release(&sb);
+	return buf;
 }
 
 char *git_pathdup(const char *fmt, ...)
 {
-	char path[PATH_MAX], *ret;
+	struct strbuf path = STRBUF_INIT;
 	va_list args;
 	va_start(args, fmt);
-	ret = vsnpath(path, sizeof(path), fmt, args);
+	vsnpath(&path, fmt, args);
 	va_end(args);
-	return xstrdup(ret);
+	return strbuf_detach(&path, NULL);
 }
 
 char *mkpathdup(const char *fmt, ...)
 {
-	char *path;
 	struct strbuf sb = STRBUF_INIT;
 	va_list args;
-
 	va_start(args, fmt);
 	strbuf_vaddf(&sb, fmt, args);
 	va_end(args);
-	path = xstrdup(cleanup_path(sb.buf));
-
-	strbuf_release(&sb);
-	return path;
+	strbuf_cleanup_path(&sb);
+	return strbuf_detach(&sb, NULL);
 }
 
 char *mkpath(const char *fmt, ...)
 {
 	va_list args;
-	unsigned len;
-	char *pathname = get_pathname();
-
+	struct strbuf *pathname = get_pathname();
 	va_start(args, fmt);
-	len = vsnprintf(pathname, PATH_MAX, fmt, args);
+	strbuf_vaddf(pathname, fmt, args);
 	va_end(args);
-	if (len >= PATH_MAX)
-		return bad_path;
-	return cleanup_path(pathname);
+	return cleanup_path(pathname->buf);
 }
 
 char *git_path(const char *fmt, ...)
 {
-	char *pathname = get_pathname();
+	struct strbuf *pathname = get_pathname();
 	va_list args;
-	char *ret;
-
 	va_start(args, fmt);
-	ret = vsnpath(pathname, PATH_MAX, fmt, args);
+	vsnpath(pathname, fmt, args);
 	va_end(args);
-	return ret;
+	return pathname->buf;
 }
 
 void home_config_paths(char **global, char **xdg, char *file)
@@ -158,41 +154,27 @@ void home_config_paths(char **global, char **xdg, char *file)
 
 char *git_path_submodule(const char *path, const char *fmt, ...)
 {
-	char *pathname = get_pathname();
-	struct strbuf buf = STRBUF_INIT;
+	struct strbuf *buf = get_pathname();
 	const char *git_dir;
 	va_list args;
-	unsigned len;
-
-	len = strlen(path);
-	if (len > PATH_MAX-100)
-		return bad_path;
 
-	strbuf_addstr(&buf, path);
-	if (len && path[len-1] != '/')
-		strbuf_addch(&buf, '/');
-	strbuf_addstr(&buf, ".git");
+	strbuf_addstr(buf, path);
+	if (buf->len && buf->buf[buf->len - 1] != '/')
+		strbuf_addch(buf, '/');
+	strbuf_addstr(buf, ".git");
 
-	git_dir = read_gitfile(buf.buf);
+	git_dir = read_gitfile(buf->buf);
 	if (git_dir) {
-		strbuf_reset(&buf);
-		strbuf_addstr(&buf, git_dir);
+		strbuf_reset(buf);
+		strbuf_addstr(buf, git_dir);
 	}
-	strbuf_addch(&buf, '/');
-
-	if (buf.len >= PATH_MAX)
-		return bad_path;
-	memcpy(pathname, buf.buf, buf.len + 1);
-
-	strbuf_release(&buf);
-	len = strlen(pathname);
+	strbuf_addch(buf, '/');
 
 	va_start(args, fmt);
-	len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
+	strbuf_vaddf(buf, fmt, args);
 	va_end(args);
-	if (len >= PATH_MAX)
-		return bad_path;
-	return cleanup_path(pathname);
+	strbuf_cleanup_path(buf);
+	return buf->buf;
 }
 
 int validate_headref(const char *path)
-- 
1.9.1.346.ga2b5940

[PATCH v7 02/31] path.c: make get_pathname() call sites return const char *

[Nguyễn Thái Ngọc Duy]

Before the previous commit, get_pathname returns an array of PATH_MAX
length. Even if git_path() and similar functions does not use the
whole array, git_path() caller can, in theory.

After the commit, get_pathname() may return a buffer that has just
enough room for the returned string and git_path() caller should never
write beyond that.

Make git_path(), mkpath() and git_path_submodule() return a const
buffer to make sure callers do not write in it at all.

This could have been part of the previous commit, but the "const"
conversion is too much distraction from the core changes in path.c.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/checkout.c     | 2 +-
 builtin/clone.c        | 9 +++++----
 builtin/fetch.c        | 5 +++--
 builtin/fsck.c         | 4 ++--
 builtin/receive-pack.c | 2 +-
 builtin/remote.c       | 2 +-
 builtin/repack.c       | 8 +++++---
 cache.h                | 6 +++---
 fast-import.c          | 2 +-
 notes-merge.c          | 6 +++---
 path.c                 | 6 +++---
 refs.c                 | 8 ++++----
 run-command.c          | 4 ++--
 run-command.h          | 2 +-
 sha1_file.c            | 2 +-
 15 files changed, 36 insertions(+), 32 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 463cfee..3abcef1 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -585,7 +585,7 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
 			if (opts->new_branch_log && !log_all_ref_updates) {
 				int temp;
 				char log_file[PATH_MAX];
-				char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
+				const char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 
 				temp = log_all_ref_updates;
 				log_all_ref_updates = 1;
diff --git a/builtin/clone.c b/builtin/clone.c
index e15ca33..91fac9d 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -289,16 +289,17 @@ static void copy_alternates(struct strbuf *src, struct strbuf *dst,
 	struct strbuf line = STRBUF_INIT;
 
 	while (strbuf_getline(&line, in, '\n') != EOF) {
-		char *abs_path, abs_buf[PATH_MAX];
+		char *abs_path;
 		if (!line.len || line.buf[0] == '#')
 			continue;
 		if (is_absolute_path(line.buf)) {
 			add_to_alternates_file(line.buf);
 			continue;
 		}
-		abs_path = mkpath("%s/objects/%s", src_repo, line.buf);
-		normalize_path_copy(abs_buf, abs_path);
-		add_to_alternates_file(abs_buf);
+		abs_path = mkpathdup("%s/objects/%s", src_repo, line.buf);
+		normalize_path_copy(abs_path, abs_path);
+		add_to_alternates_file(abs_path);
+		free(abs_path);
 	}
 	strbuf_release(&line);
 	fclose(in);
diff --git a/builtin/fetch.c b/builtin/fetch.c
index e8d0cca..9522b1b 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -573,7 +573,8 @@ static int store_updated_refs(const char *raw_url, const char *remote_name,
 	struct strbuf note = STRBUF_INIT;
 	const char *what, *kind;
 	struct ref *rm;
-	char *url, *filename = dry_run ? "/dev/null" : git_path("FETCH_HEAD");
+	char *url;
+	const char *filename = dry_run ? "/dev/null" : git_path("FETCH_HEAD");
 	int want_status;
 
 	fp = fopen(filename, "a");
@@ -807,7 +808,7 @@ static void check_not_current_branch(struct ref *ref_map)
 
 static int truncate_fetch_head(void)
 {
-	char *filename = git_path("FETCH_HEAD");
+	const char *filename = git_path("FETCH_HEAD");
 	FILE *fp = fopen(filename, "w");
 
 	if (!fp)
diff --git a/builtin/fsck.c b/builtin/fsck.c
index 8aadca1..d414962 100644
--- a/builtin/fsck.c
+++ b/builtin/fsck.c
@@ -225,12 +225,12 @@ static void check_unreachable_object(struct object *obj)
 			printf("dangling %s %s\n", typename(obj->type),
 			       sha1_to_hex(obj->sha1));
 		if (write_lost_and_found) {
-			char *filename = git_path("lost-found/%s/%s",
+			const char *filename = git_path("lost-found/%s/%s",
 				obj->type == OBJ_COMMIT ? "commit" : "other",
 				sha1_to_hex(obj->sha1));
 			FILE *f;
 
-			if (safe_create_leading_directories(filename)) {
+			if (safe_create_leading_directories_const(filename)) {
 				error("Could not create lost-found");
 				return;
 			}
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 18458e8..ed11e7e 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -599,7 +599,7 @@ static void run_update_post_hook(struct command *commands)
 	int argc;
 	const char **argv;
 	struct child_process proc;
-	char *hook;
+	const char *hook;
 
 	hook = find_hook("post-update");
 	for (argc = 0, cmd = commands; cmd; cmd = cmd->next) {
diff --git a/builtin/remote.c b/builtin/remote.c
index a8efe3d..3d99c9c 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -580,7 +580,7 @@ static int migrate_file(struct remote *remote)
 {
 	struct strbuf buf = STRBUF_INIT;
 	int i;
-	char *path = NULL;
+	const char *path = NULL;
 
 	strbuf_addf(&buf, "remote.%s.url", remote->name);
 	for (i = 0; i < remote->url_nr; i++)
diff --git a/builtin/repack.c b/builtin/repack.c
index ff2216a..a64a4a9 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -285,7 +285,8 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	failed = 0;
 	for_each_string_list_item(item, &names) {
 		for (ext = 0; ext < ARRAY_SIZE(exts); ext++) {
-			char *fname, *fname_old;
+			const char *fname_old;
+			char *fname;
 			fname = mkpathdup("%s/pack-%s%s", packdir,
 						item->string, exts[ext].name);
 			if (!file_exists(fname)) {
@@ -313,7 +314,8 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	if (failed) {
 		struct string_list rollback_failure = STRING_LIST_INIT_DUP;
 		for_each_string_list_item(item, &rollback) {
-			char *fname, *fname_old;
+			const char *fname_old;
+			char *fname;
 			fname = mkpathdup("%s/%s", packdir, item->string);
 			fname_old = mkpath("%s/old-%s", packdir, item->string);
 			if (rename(fname_old, fname))
@@ -366,7 +368,7 @@ int cmd_repack(int argc, const char **argv, const char *prefix)
 	/* Remove the "old-" files */
 	for_each_string_list_item(item, &names) {
 		for (ext = 0; ext < ARRAY_SIZE(exts); ext++) {
-			char *fname;
+			const char *fname;
 			fname = mkpath("%s/old-%s%s",
 					packdir,
 					item->string,
diff --git a/cache.h b/cache.h
index 44aa439..707408b 100644
--- a/cache.h
+++ b/cache.h
@@ -682,9 +682,9 @@ extern char *mkpathdup(const char *fmt, ...)
 	__attribute__((format (printf, 1, 2)));
 
 /* Return a statically allocated filename matching the sha1 signature */
-extern char *mkpath(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
-extern char *git_path(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
-extern char *git_path_submodule(const char *path, const char *fmt, ...)
+extern const char *mkpath(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
+extern const char *git_path(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
+extern const char *git_path_submodule(const char *path, const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
 
 /*
diff --git a/fast-import.c b/fast-import.c
index fa635f7..d9c068b 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -404,7 +404,7 @@ static void dump_marks_helper(FILE *, uintmax_t, struct mark_set *);
 
 static void write_crash_report(const char *err)
 {
-	char *loc = git_path("fast_import_crash_%"PRIuMAX, (uintmax_t) getpid());
+	const char *loc = git_path("fast_import_crash_%"PRIuMAX, (uintmax_t) getpid());
 	FILE *rpt = fopen(loc, "w");
 	struct branch *b;
 	unsigned long lu;
diff --git a/notes-merge.c b/notes-merge.c
index fd5fae2..a9e6b15 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -280,7 +280,7 @@ static void check_notes_merge_worktree(struct notes_merge_options *o)
 				    "(%s exists).", git_path("NOTES_MERGE_*"));
 		}
 
-		if (safe_create_leading_directories(git_path(
+		if (safe_create_leading_directories_const(git_path(
 				NOTES_MERGE_WORKTREE "/.test")))
 			die_errno("unable to create directory %s",
 				  git_path(NOTES_MERGE_WORKTREE));
@@ -295,8 +295,8 @@ static void write_buf_to_worktree(const unsigned char *obj,
 				  const char *buf, unsigned long size)
 {
 	int fd;
-	char *path = git_path(NOTES_MERGE_WORKTREE "/%s", sha1_to_hex(obj));
-	if (safe_create_leading_directories(path))
+	const char *path = git_path(NOTES_MERGE_WORKTREE "/%s", sha1_to_hex(obj));
+	if (safe_create_leading_directories_const(path))
 		die_errno("unable to create directory for '%s'", path);
 	if (file_exists(path))
 		die("found existing file at '%s'", path);
diff --git a/path.c b/path.c
index 42ef3af..a3f8826 100644
--- a/path.c
+++ b/path.c
@@ -106,7 +106,7 @@ char *mkpathdup(const char *fmt, ...)
 	return strbuf_detach(&sb, NULL);
 }
 
-char *mkpath(const char *fmt, ...)
+const char *mkpath(const char *fmt, ...)
 {
 	va_list args;
 	struct strbuf *pathname = get_pathname();
@@ -116,7 +116,7 @@ char *mkpath(const char *fmt, ...)
 	return cleanup_path(pathname->buf);
 }
 
-char *git_path(const char *fmt, ...)
+const char *git_path(const char *fmt, ...)
 {
 	struct strbuf *pathname = get_pathname();
 	va_list args;
@@ -152,7 +152,7 @@ void home_config_paths(char **global, char **xdg, char *file)
 	free(to_free);
 }
 
-char *git_path_submodule(const char *path, const char *fmt, ...)
+const char *git_path_submodule(const char *path, const char *fmt, ...)
 {
 	struct strbuf *buf = get_pathname();
 	const char *git_dir;
diff --git a/refs.c b/refs.c
index 82e4842..dbd131e 100644
--- a/refs.c
+++ b/refs.c
@@ -1442,7 +1442,7 @@ static int resolve_gitlink_ref_recursive(struct ref_cache *refs,
 {
 	int fd, len;
 	char buffer[128], *p;
-	char *path;
+	const char *path;
 
 	if (recursion > MAXDEPTH || strlen(refname) > MAXREFLEN)
 		return -1;
@@ -2255,7 +2255,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 					    const unsigned char *old_sha1,
 					    int flags, int *type_p)
 {
-	char *ref_file;
+	const char *ref_file;
 	const char *orig_refname = refname;
 	struct ref_lock *lock;
 	int last_errno = 0;
@@ -2318,7 +2318,7 @@ static struct ref_lock *lock_ref_sha1_basic(const char *refname,
 		lock->force_write = 1;
 
  retry:
-	switch (safe_create_leading_directories(ref_file)) {
+	switch (safe_create_leading_directories_const(ref_file)) {
 	case SCLD_OK:
 		break; /* success */
 	case SCLD_VANISHED:
@@ -2756,7 +2756,7 @@ static int rename_tmp_log(const char *newrefname)
 	int attempts_remaining = 4;
 
  retry:
-	switch (safe_create_leading_directories(git_path("logs/%s", newrefname))) {
+	switch (safe_create_leading_directories_const(git_path("logs/%s", newrefname))) {
 	case SCLD_OK:
 		break; /* success */
 	case SCLD_VANISHED:
diff --git a/run-command.c b/run-command.c
index be07d4a..614b8ac 100644
--- a/run-command.c
+++ b/run-command.c
@@ -758,9 +758,9 @@ int finish_async(struct async *async)
 #endif
 }
 
-char *find_hook(const char *name)
+const char *find_hook(const char *name)
 {
-	char *path = git_path("hooks/%s", name);
+	const char *path = git_path("hooks/%s", name);
 	if (access(path, X_OK) < 0)
 		path = NULL;
 
diff --git a/run-command.h b/run-command.h
index ea73de3..890cc95 100644
--- a/run-command.h
+++ b/run-command.h
@@ -48,7 +48,7 @@ int start_command(struct child_process *);
 int finish_command(struct child_process *);
 int run_command(struct child_process *);
 
-extern char *find_hook(const char *name);
+extern const char *find_hook(const char *name);
 LAST_ARG_MUST_BE_NULL
 extern int run_hook_le(const char *const *env, const char *name, ...);
 extern int run_hook_ve(const char *const *env, const char *name, va_list args);
diff --git a/sha1_file.c b/sha1_file.c
index a38854c..9700108 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -402,7 +402,7 @@ void add_to_alternates_file(const char *reference)
 {
 	struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
 	int fd = hold_lock_file_for_append(lock, git_path("objects/info/alternates"), LOCK_DIE_ON_ERROR);
-	char *alt = mkpath("%s\n", reference);
+	const char *alt = mkpath("%s\n", reference);
 	write_or_die(fd, alt, strlen(alt));
 	if (commit_lock_file(lock))
 		die("could not close alternates file");
-- 
1.9.1.346.ga2b5940

[PATCH v7 03/31] git_snpath(): retire and replace with strbuf_git_path()

[Nguyễn Thái Ngọc Duy]

In the previous patch, git_snpath() is modified to allocate a new
strbuf buffer because vsnpath() needs that. But that makes it
awkward because git_snpath() receives a pre-allocated buffer from
outside and has to copy data back. Rename it to strbuf_git_path()
and make it receive strbuf directly.

Using git_path() in update_refs_for_switch() which used to call
git_snpath() is safe because that function and all of its callers do
not keep any pointer to the round-robin buffer pool allocated by
get_pathname().

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/checkout.c | 13 +++++----
 cache.h            |  4 +--
 path.c             | 11 ++------
 refs.c             | 78 +++++++++++++++++++++++++++++++++---------------------
 refs.h             |  2 +-
 5 files changed, 61 insertions(+), 47 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 3abcef1..8023987 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -584,18 +584,21 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
 		if (opts->new_orphan_branch) {
 			if (opts->new_branch_log && !log_all_ref_updates) {
 				int temp;
-				char log_file[PATH_MAX];
-				const char *ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
+				struct strbuf log_file = STRBUF_INIT;
+				int ret;
+				const char *ref_name;
 
+				ref_name = mkpath("refs/heads/%s", opts->new_orphan_branch);
 				temp = log_all_ref_updates;
 				log_all_ref_updates = 1;
-				if (log_ref_setup(ref_name, log_file, sizeof(log_file))) {
+				ret = log_ref_setup(ref_name, &log_file);
+				log_all_ref_updates = temp;
+				strbuf_release(&log_file);
+				if (ret) {
 					fprintf(stderr, _("Can not do reflog for '%s'\n"),
 					    opts->new_orphan_branch);
-					log_all_ref_updates = temp;
 					return;
 				}
-				log_all_ref_updates = temp;
 			}
 		}
 		else
diff --git a/cache.h b/cache.h
index 707408b..279b581 100644
--- a/cache.h
+++ b/cache.h
@@ -674,8 +674,8 @@ extern int check_repository_format(void);
 
 extern char *mksnpath(char *buf, size_t n, const char *fmt, ...)
 	__attribute__((format (printf, 3, 4)));
-extern char *git_snpath(char *buf, size_t n, const char *fmt, ...)
-	__attribute__((format (printf, 3, 4)));
+extern void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
+	__attribute__((format (printf, 2, 3)));
 extern char *git_pathdup(const char *fmt, ...)
 	__attribute__((format (printf, 1, 2)));
 extern char *mkpathdup(const char *fmt, ...)
diff --git a/path.c b/path.c
index a3f8826..e545064 100644
--- a/path.c
+++ b/path.c
@@ -70,19 +70,12 @@ static void vsnpath(struct strbuf *buf, const char *fmt, va_list args)
 	strbuf_cleanup_path(buf);
 }
 
-char *git_snpath(char *buf, size_t n, const char *fmt, ...)
+void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 {
-	struct strbuf sb = STRBUF_INIT;
 	va_list args;
 	va_start(args, fmt);
-	vsnpath(&sb, fmt, args);
+	vsnpath(sb, fmt, args);
 	va_end(args);
-	if (sb.len >= n)
-		strlcpy(buf, bad_path, n);
-	else
-		memcpy(buf, sb.buf, sb.len + 1);
-	strbuf_release(&sb);
-	return buf;
 }
 
 char *git_pathdup(const char *fmt, ...)
diff --git a/refs.c b/refs.c
index dbd131e..00b2312 100644
--- a/refs.c
+++ b/refs.c
@@ -1535,10 +1535,12 @@ static const char *handle_missing_loose_ref(const char *refname,
 
 const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int reading, int *flag)
 {
+	struct strbuf sb_path = STRBUF_INIT;
 	int depth = MAXDEPTH;
 	ssize_t len;
 	char buffer[256];
 	static char refname_buffer[256];
+	const char *ret;
 
 	if (flag)
 		*flag = 0;
@@ -1547,15 +1549,17 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 		return NULL;
 
 	for (;;) {
-		char path[PATH_MAX];
+		const char *path;
 		struct stat st;
 		char *buf;
 		int fd;
 
 		if (--depth < 0)
-			return NULL;
+			goto fail;
 
-		git_snpath(path, sizeof(path), "%s", refname);
+		strbuf_reset(&sb_path);
+		strbuf_git_path(&sb_path, "%s", refname);
+		path = sb_path.buf;
 
 		/*
 		 * We might have to loop back here to avoid a race
@@ -1569,10 +1573,11 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 	stat_ref:
 		if (lstat(path, &st) < 0) {
 			if (errno == ENOENT)
-				return handle_missing_loose_ref(refname, sha1,
-								reading, flag);
+				ret = handle_missing_loose_ref(refname, sha1,
+							       reading, flag);
 			else
-				return NULL;
+				ret = NULL;
+			goto done;
 		}
 
 		/* Follow "normalized" - ie "refs/.." symlinks by hand */
@@ -1583,7 +1588,7 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 					/* inconsistent with lstat; retry */
 					goto stat_ref;
 				else
-					return NULL;
+					goto fail;
 			}
 			buffer[len] = 0;
 			if (starts_with(buffer, "refs/") &&
@@ -1599,7 +1604,7 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 		/* Is it a directory? */
 		if (S_ISDIR(st.st_mode)) {
 			errno = EISDIR;
-			return NULL;
+			goto fail;
 		}
 
 		/*
@@ -1612,12 +1617,13 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 				/* inconsistent with lstat; retry */
 				goto stat_ref;
 			else
-				return NULL;
+				goto fail;
 		}
+
 		len = read_in_full(fd, buffer, sizeof(buffer)-1);
 		close(fd);
 		if (len < 0)
-			return NULL;
+			goto fail;
 		while (len && isspace(buffer[len-1]))
 			len--;
 		buffer[len] = '\0';
@@ -1634,9 +1640,10 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 			    (buffer[40] != '\0' && !isspace(buffer[40]))) {
 				if (flag)
 					*flag |= REF_ISBROKEN;
-				return NULL;
+				goto fail;
 			}
-			return refname;
+			ret = refname;
+			goto done;
 		}
 		if (flag)
 			*flag |= REF_ISSYMREF;
@@ -1646,10 +1653,15 @@ const char *resolve_ref_unsafe(const char *refname, unsigned char *sha1, int rea
 		if (check_refname_format(buf, REFNAME_ALLOW_ONELEVEL)) {
 			if (flag)
 				*flag |= REF_ISBROKEN;
-			return NULL;
+			goto fail;
 		}
 		refname = strcpy(refname_buffer, buf);
 	}
+fail:
+	ret = NULL;
+done:
+	strbuf_release(&sb_path);
+	return ret;
 }
 
 char *resolve_refdup(const char *ref, unsigned char *sha1, int reading, int *flag)
@@ -2940,41 +2952,41 @@ static int copy_msg(char *buf, const char *msg)
 	return cp - buf;
 }
 
-int log_ref_setup(const char *refname, char *logfile, int bufsize)
+int log_ref_setup(const char *refname, struct strbuf *logfile)
 {
 	int logfd, oflags = O_APPEND | O_WRONLY;
 
-	git_snpath(logfile, bufsize, "logs/%s", refname);
+	strbuf_git_path(logfile, "logs/%s", refname);
 	if (log_all_ref_updates &&
 	    (starts_with(refname, "refs/heads/") ||
 	     starts_with(refname, "refs/remotes/") ||
 	     starts_with(refname, "refs/notes/") ||
 	     !strcmp(refname, "HEAD"))) {
-		if (safe_create_leading_directories(logfile) < 0)
+		if (safe_create_leading_directories(logfile->buf) < 0)
 			return error("unable to create directory for %s",
-				     logfile);
+				     logfile->buf);
 		oflags |= O_CREAT;
 	}
 
-	logfd = open(logfile, oflags, 0666);
+	logfd = open(logfile->buf, oflags, 0666);
 	if (logfd < 0) {
 		if (!(oflags & O_CREAT) && errno == ENOENT)
 			return 0;
 
 		if ((oflags & O_CREAT) && errno == EISDIR) {
-			if (remove_empty_directories(logfile)) {
+			if (remove_empty_directories(logfile->buf)) {
 				return error("There are still logs under '%s'",
-					     logfile);
+					     logfile->buf);
 			}
-			logfd = open(logfile, oflags, 0666);
+			logfd = open(logfile->buf, oflags, 0666);
 		}
 
 		if (logfd < 0)
 			return error("Unable to append to %s: %s",
-				     logfile, strerror(errno));
+				     logfile->buf, strerror(errno));
 	}
 
-	adjust_shared_perm(logfile);
+	adjust_shared_perm(logfile->buf);
 	close(logfd);
 	return 0;
 }
@@ -2985,20 +2997,22 @@ static int log_ref_write(const char *refname, const unsigned char *old_sha1,
 	int logfd, result, written, oflags = O_APPEND | O_WRONLY;
 	unsigned maxlen, len;
 	int msglen;
-	char log_file[PATH_MAX];
+	struct strbuf sb_log_file = STRBUF_INIT;
+	const char *log_file;
 	char *logrec;
 	const char *committer;
 
 	if (log_all_ref_updates < 0)
 		log_all_ref_updates = !is_bare_repository();
 
-	result = log_ref_setup(refname, log_file, sizeof(log_file));
+	result = log_ref_setup(refname, &sb_log_file);
 	if (result)
-		return result;
+		goto done;
+	log_file = sb_log_file.buf;
 
 	logfd = open(log_file, oflags);
 	if (logfd < 0)
-		return 0;
+		goto done;
 	msglen = msg ? strlen(msg) : 0;
 	committer = git_committer_info(0);
 	maxlen = strlen(committer) + msglen + 100;
@@ -3011,9 +3025,13 @@ static int log_ref_write(const char *refname, const unsigned char *old_sha1,
 		len += copy_msg(logrec + len - 1, msg) - 1;
 	written = len <= maxlen ? write_in_full(logfd, logrec, len) : -1;
 	free(logrec);
-	if (close(logfd) != 0 || written != len)
-		return error("Unable to append to %s", log_file);
-	return 0;
+	if (close(logfd) != 0 || written != len) {
+		error("Unable to append to %s", log_file);
+		result = -1;
+	}
+done:
+	strbuf_release(&sb_log_file);
+	return result;
 }
 
 static int is_branch(const char *refname)
diff --git a/refs.h b/refs.h
index 4e3050d..99d88a7 100644
--- a/refs.h
+++ b/refs.h
@@ -157,7 +157,7 @@ extern void unlock_ref(struct ref_lock *lock);
 extern int write_ref_sha1(struct ref_lock *lock, const unsigned char *sha1, const char *msg);
 
 /** Setup reflog before using. **/
-int log_ref_setup(const char *refname, char *logfile, int bufsize);
+int log_ref_setup(const char *refname, struct strbuf *logfile);
 
 /** Reads log for the value of ref during at_time. **/
 extern int read_ref_at(const char *refname, unsigned long at_time, int cnt,
-- 
1.9.1.346.ga2b5940

[PATCH v7 04/31] path.c: rename vsnpath() to do_git_path()

[Nguyễn Thái Ngọc Duy]

The name vsnpath() gives an impression that this is general path
handling function. It's not. This is the underlying implementation of
git_path(), git_pathdup() and strbuf_git_path() which will prefix
$GIT_DIR in the result string.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 path.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/path.c b/path.c
index e545064..2cb2e61 100644
--- a/path.c
+++ b/path.c
@@ -60,7 +60,7 @@ char *mksnpath(char *buf, size_t n, const char *fmt, ...)
 	return cleanup_path(buf);
 }
 
-static void vsnpath(struct strbuf *buf, const char *fmt, va_list args)
+static void do_git_path(struct strbuf *buf, const char *fmt, va_list args)
 {
 	const char *git_dir = get_git_dir();
 	strbuf_addstr(buf, git_dir);
@@ -74,7 +74,7 @@ void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 {
 	va_list args;
 	va_start(args, fmt);
-	vsnpath(sb, fmt, args);
+	do_git_path(sb, fmt, args);
 	va_end(args);
 }
 
@@ -83,7 +83,7 @@ char *git_pathdup(const char *fmt, ...)
 	struct strbuf path = STRBUF_INIT;
 	va_list args;
 	va_start(args, fmt);
-	vsnpath(&path, fmt, args);
+	do_git_path(&path, fmt, args);
 	va_end(args);
 	return strbuf_detach(&path, NULL);
 }
@@ -114,7 +114,7 @@ const char *git_path(const char *fmt, ...)
 	struct strbuf *pathname = get_pathname();
 	va_list args;
 	va_start(args, fmt);
-	vsnpath(pathname, fmt, args);
+	do_git_path(pathname, fmt, args);
 	va_end(args);
 	return pathname->buf;
 }
-- 
1.9.1.346.ga2b5940

[PATCH v7 05/31] path.c: group git_path(), git_pathdup() and strbuf_git_path() together

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 path.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/path.c b/path.c
index 2cb2e61..65881aa 100644
--- a/path.c
+++ b/path.c
@@ -78,6 +78,16 @@ void strbuf_git_path(struct strbuf *sb, const char *fmt, ...)
 	va_end(args);
 }
 
+const char *git_path(const char *fmt, ...)
+{
+	struct strbuf *pathname = get_pathname();
+	va_list args;
+	va_start(args, fmt);
+	do_git_path(pathname, fmt, args);
+	va_end(args);
+	return pathname->buf;
+}
+
 char *git_pathdup(const char *fmt, ...)
 {
 	struct strbuf path = STRBUF_INIT;
@@ -109,16 +119,6 @@ const char *mkpath(const char *fmt, ...)
 	return cleanup_path(pathname->buf);
 }
 
-const char *git_path(const char *fmt, ...)
-{
-	struct strbuf *pathname = get_pathname();
-	va_list args;
-	va_start(args, fmt);
-	do_git_path(pathname, fmt, args);
-	va_end(args);
-	return pathname->buf;
-}
-
 void home_config_paths(char **global, char **xdg, char *file)
 {
 	char *xdg_home = getenv("XDG_CONFIG_HOME");
-- 
1.9.1.346.ga2b5940

[PATCH v7 06/31] git_path(): be aware of file relocation in $GIT_DIR

[Nguyễn Thái Ngọc Duy]

We allow the user to relocate certain paths out of $GIT_DIR via
environment variables, e.g. GIT_OBJECT_DIRECTORY, GIT_INDEX_FILE and
GIT_GRAFT_FILE. Callers are not supposed to use git_path() or
git_pathdup() to get those paths. Instead they must use
get_object_directory(), get_index_file() and get_graft_file()
respectively. This is inconvenient and could be missed in review (for
example, there's git_path("objects/info/alternates") somewhere in
sha1_file.c).

This patch makes git_path() and git_pathdup() understand those
environment variables. So if you set GIT_OBJECT_DIRECTORY to /foo/bar,
git_path("objects/abc") should return /foo/bar/abc. The same is done
for the two remaining env variables.

"git rev-parse --git-path" is the wrapper for script use.

This patch kinda reverts a0279e1 (setup_git_env: use git_pathdup
instead of xmalloc + sprintf - 2014-06-19) because using git_pathdup
here would result in infinite recursion:

  setup_git_env() -> git_pathdup("objects") -> .. -> adjust_git_path()
  -> get_object_directory() -> oops, git_object_directory is NOT set
  yet -> setup_git_env()

I wanted to make git_pathdup_literal() that skips adjust_git_path().
But that won't work because later on when $GIT_COMMON_DIR is
introduced, git_pathdup_literal("objects") needs adjust_git_path() to
replace $GIT_DIR with $GIT_COMMON_DIR.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git-rev-parse.txt |  7 ++++++
 builtin/rev-parse.c             |  7 ++++++
 cache.h                         |  1 +
 environment.c                   | 19 +++++++++++-----
 path.c                          | 49 +++++++++++++++++++++++++++++++++++++++--
 t/t0060-path-utils.sh           | 19 ++++++++++++++++
 6 files changed, 95 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index 987395d..9465399 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -232,6 +232,13 @@ print a message to stderr and exit with nonzero status.
 	repository.  If <path> is a gitfile then the resolved path
 	to the real repository is printed.
 
+--git-path <path>::
+	Resolve "$GIT_DIR/<path>" and takes other path relocation
+	variables such as $GIT_OBJECT_DIRECTORY,
+	$GIT_INDEX_FILE... into account. For example, if
+	$GIT_OBJECT_DIRECTORY is set to /foo/bar then "git rev-parse
+	--git-path objects/abc" returns /foo/bar/abc.
+
 --show-cdup::
 	When the command is invoked from a subdirectory, show the
 	path of the top-level directory relative to the current
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 1a6122d..7606d43 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -529,6 +529,13 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
 
+		if (!strcmp(arg, "--git-path")) {
+			if (!argv[i + 1])
+				die("--git-path requires an argument");
+			puts(git_path("%s", argv[i + 1]));
+			i++;
+			continue;
+		}
 		if (as_is) {
 			if (show_file(arg, output_prefix) && as_is < 2)
 				verify_filename(prefix, arg, 0);
diff --git a/cache.h b/cache.h
index 279b581..0128b9a 100644
--- a/cache.h
+++ b/cache.h
@@ -612,6 +612,7 @@ extern int fsync_object_files;
 extern int core_preload_index;
 extern int core_apply_sparse_checkout;
 extern int precomposed_unicode;
+extern int git_db_env, git_index_env, git_graft_env;
 
 /*
  * The character that begins a commented line in user-editable file
diff --git a/environment.c b/environment.c
index 565f652..fee12a6 100644
--- a/environment.c
+++ b/environment.c
@@ -83,6 +83,7 @@ static size_t namespace_len;
 
 static const char *git_dir;
 static char *git_object_dir, *git_index_file, *git_graft_file;
+int git_db_env, git_index_env, git_graft_env;
 
 /*
  * Repository-local GIT_* environment variables; see cache.h for details.
@@ -124,10 +125,18 @@ static char *expand_namespace(const char *raw_namespace)
 	return strbuf_detach(&buf, NULL);
 }
 
-static char *git_path_from_env(const char *envvar, const char *path)
+static char *git_path_from_env(const char *envvar, const char *path,
+			       int *fromenv)
 {
 	const char *value = getenv(envvar);
-	return value ? xstrdup(value) : git_pathdup("%s", path);
+	if (!value) {
+		char *buf = xmalloc(strlen(git_dir) + strlen(path) + 2);
+		sprintf(buf, "%s/%s", git_dir, path);
+		return buf;
+	}
+	if (fromenv)
+		*fromenv = 1;
+	return xstrdup(value);
 }
 
 static void setup_git_env(void)
@@ -140,9 +149,9 @@ static void setup_git_env(void)
 		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
 	gitfile = read_gitfile(git_dir);
 	git_dir = xstrdup(gitfile ? gitfile : git_dir);
-	git_object_dir = git_path_from_env(DB_ENVIRONMENT, "objects");
-	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, "index");
-	git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, "info/grafts");
+	git_object_dir = git_path_from_env(DB_ENVIRONMENT, "objects", &git_db_env);
+	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, "index", &git_index_env);
+	git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, "info/grafts", &git_graft_env);
 	if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
 		check_replace_refs = 0;
 	namespace = expand_namespace(getenv(GIT_NAMESPACE_ENVIRONMENT));
diff --git a/path.c b/path.c
index 65881aa..3deb80c 100644
--- a/path.c
+++ b/path.c
@@ -60,13 +60,58 @@ char *mksnpath(char *buf, size_t n, const char *fmt, ...)
 	return cleanup_path(buf);
 }
 
+static int dir_prefix(const char *buf, const char *dir)
+{
+	int len = strlen(dir);
+	return !strncmp(buf, dir, len) &&
+		(is_dir_sep(buf[len]) || buf[len] == '\0');
+}
+
+/* $buf =~ m|$dir/+$file| but without regex */
+static int is_dir_file(const char *buf, const char *dir, const char *file)
+{
+	int len = strlen(dir);
+	if (strncmp(buf, dir, len) || !is_dir_sep(buf[len]))
+		return 0;
+	while (is_dir_sep(buf[len]))
+		len++;
+	return !strcmp(buf + len, file);
+}
+
+static void replace_dir(struct strbuf *buf, int len, const char *newdir)
+{
+	int newlen = strlen(newdir);
+	int need_sep = (buf->buf[len] && !is_dir_sep(buf->buf[len])) &&
+		!is_dir_sep(newdir[newlen - 1]);
+	if (need_sep)
+		len--;	 /* keep one char, to be replaced with '/'  */
+	strbuf_splice(buf, 0, len, newdir, newlen);
+	if (need_sep)
+		buf->buf[newlen] = '/';
+}
+
+static void adjust_git_path(struct strbuf *buf, int git_dir_len)
+{
+	const char *base = buf->buf + git_dir_len;
+	if (git_graft_env && is_dir_file(base, "info", "grafts"))
+		strbuf_splice(buf, 0, buf->len,
+			      get_graft_file(), strlen(get_graft_file()));
+	else if (git_index_env && !strcmp(base, "index"))
+		strbuf_splice(buf, 0, buf->len,
+			      get_index_file(), strlen(get_index_file()));
+	else if (git_db_env && dir_prefix(base, "objects"))
+		replace_dir(buf, git_dir_len + 7, get_object_directory());
+}
+
 static void do_git_path(struct strbuf *buf, const char *fmt, va_list args)
 {
-	const char *git_dir = get_git_dir();
-	strbuf_addstr(buf, git_dir);
+	int gitdir_len;
+	strbuf_addstr(buf, get_git_dir());
 	if (buf->len && !is_dir_sep(buf->buf[buf->len - 1]))
 		strbuf_addch(buf, '/');
+	gitdir_len = buf->len;
 	strbuf_vaddf(buf, fmt, args);
+	adjust_git_path(buf, gitdir_len);
 	strbuf_cleanup_path(buf);
 }
 
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index c0143a0..33d2818 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -19,6 +19,14 @@ relative_path() {
 	"test \"\$(test-path-utils relative_path '$1' '$2')\" = '$expected'"
 }
 
+test_git_path() {
+	test_expect_success "git-path $1 $2 => $3" "
+		$1 git rev-parse --git-path $2 >actual &&
+		echo $3 >expect &&
+		test_cmp expect actual
+	"
+}
+
 # On Windows, we are using MSYS's bash, which mangles the paths.
 # Absolute paths are anchored at the MSYS installation directory,
 # which means that the path / accounts for this many characters:
@@ -244,4 +252,15 @@ relative_path "<null>"		"<empty>"	./
 relative_path "<null>"		"<null>"	./
 relative_path "<null>"		/foo/a/b	./
 
+test_git_path A=B                info/grafts .git/info/grafts
+test_git_path GIT_GRAFT_FILE=foo info/grafts foo
+test_git_path GIT_GRAFT_FILE=foo info/////grafts foo
+test_git_path GIT_INDEX_FILE=foo index foo
+test_git_path GIT_INDEX_FILE=foo index/foo .git/index/foo
+test_git_path GIT_INDEX_FILE=foo index2 .git/index2
+test_expect_success 'setup fake objects directory foo' 'mkdir foo'
+test_git_path GIT_OBJECT_DIRECTORY=foo objects foo
+test_git_path GIT_OBJECT_DIRECTORY=foo objects/foo foo/foo
+test_git_path GIT_OBJECT_DIRECTORY=foo objects2 .git/objects2
+
 test_done
-- 
1.9.1.346.ga2b5940

[PATCH v7 07/31] *.sh: respect $GIT_INDEX_FILE

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 git-pull.sh  | 2 +-
 git-stash.sh | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/git-pull.sh b/git-pull.sh
index 18a394f..6ab0c31 100755
--- a/git-pull.sh
+++ b/git-pull.sh
@@ -240,7 +240,7 @@ test true = "$rebase" && {
 	if ! git rev-parse -q --verify HEAD >/dev/null
 	then
 		# On an unborn branch
-		if test -f "$GIT_DIR/index"
+		if test -f "$(git rev-parse --git-path index)"
 		then
 			die "$(gettext "updating an unborn branch with changes added to the index")"
 		fi
diff --git a/git-stash.sh b/git-stash.sh
index bcc757b..393e1ec 100755
--- a/git-stash.sh
+++ b/git-stash.sh
@@ -20,7 +20,7 @@ require_work_tree
 cd_to_toplevel
 
 TMP="$GIT_DIR/.git-stash.$$"
-TMPindex=${GIT_INDEX_FILE-"$GIT_DIR/index"}.stash.$$
+TMPindex=${GIT_INDEX_FILE-"$(git rev-parse --git-path index)"}.stash.$$
 trap 'rm -f "$TMP-"* "$TMPindex"' 0
 
 ref_stash=refs/stash
-- 
1.9.1.346.ga2b5940

[PATCH v7 08/31] reflog: avoid constructing .lock path with git_path

[Nguyễn Thái Ngọc Duy]

Among pathnames in $GIT_DIR, e.g. "index" or "packed-refs", we want to
automatically and silently map some of them to the $GIT_DIR of the
repository we are borrowing from via $GIT_COMMON_DIR mechanism.  When
we formulate the pathname for its lockfile, we want it to be in the
same location as its final destination.  "index" is not shared and
needs to remain in the borrowing repository, while "packed-refs" is
shared and needs to go to the borrowed repository.

git_path() could be taught about the ".lock" suffix and map
"index.lock" and "packed-refs.lock" the same way their basenames are
mapped, but instead the caller can help by asking where the basename
(e.g. "index") is mapped to git_path() and then appending ".lock"
after the mapping is done.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/reflog.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/reflog.c b/builtin/reflog.c
index e8a8fb1..9bd874d 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c
@@ -372,7 +372,7 @@ static int expire_reflog(const char *ref, const unsigned char *sha1, int unused,
 	if (!reflog_exists(ref))
 		goto finish;
 	if (!cmd->dry_run) {
-		newlog_path = git_pathdup("logs/%s.lock", ref);
+		newlog_path = mkpathdup("%s.lock", log_file);
 		cb.newlog = fopen(newlog_path, "w");
 	}
 
-- 
1.9.1.346.ga2b5940

[PATCH v7 09/31] fast-import: use git_path() for accessing .git dir instead of get_git_dir()

[Nguyễn Thái Ngọc Duy]

This allows git_path() to redirect info/fast-import to another place
if needed

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 fast-import.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/fast-import.c b/fast-import.c
index d9c068b..ea426c4 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -3103,12 +3103,9 @@ static void parse_progress(void)
 
 static char* make_fast_import_path(const char *path)
 {
-	struct strbuf abs_path = STRBUF_INIT;
-
 	if (!relative_marks_paths || is_absolute_path(path))
 		return xstrdup(path);
-	strbuf_addf(&abs_path, "%s/info/fast-import/%s", get_git_dir(), path);
-	return strbuf_detach(&abs_path, NULL);
+	return xstrdup(git_path("info/fast-import/%s", path));
 }
 
 static void option_import_marks(const char *marks,
-- 
1.9.1.346.ga2b5940

[PATCH v7 10/31] commit: use SEQ_DIR instead of hardcoding "sequencer"

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/commit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index 461c3b1..4b9f012 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -156,7 +156,7 @@ static void determine_whence(struct wt_status *s)
 		whence = FROM_MERGE;
 	else if (file_exists(git_path("CHERRY_PICK_HEAD"))) {
 		whence = FROM_CHERRY_PICK;
-		if (file_exists(git_path("sequencer")))
+		if (file_exists(git_path(SEQ_DIR)))
 			sequencer_in_use = 1;
 	}
 	else
-- 
1.9.1.346.ga2b5940

[PATCH v7 11/31] $GIT_COMMON_DIR: a new environment variable

[Nguyễn Thái Ngọc Duy]

This variable is intended to support multiple working directories
attached to a repository. Such a repository may have a main working
directory, created by either "git init" or "git clone" and one or more
linked working directories. These working directories and the main
repository share the same repository directory.

In linked working directories, $GIT_COMMON_DIR must be defined to point
to the real repository directory and $GIT_DIR points to an unused
subdirectory inside $GIT_COMMON_DIR. File locations inside the
repository are reorganized from the linked worktree view point:

 - worktree-specific such as HEAD, logs/HEAD, index, other top-level
   refs and unrecognized files are from $GIT_DIR.

 - the rest like objects, refs, info, hooks, packed-refs, shallow...
   are from $GIT_COMMON_DIR (except info/sparse-checkout, but that's
   a separate patch)

Scripts are supposed to retrieve paths in $GIT_DIR with "git rev-parse
--git-path", which will take care of "$GIT_DIR vs $GIT_COMMON_DIR"
business.

The redirection is done by git_path(), git_pathdup() and
strbuf_git_path(). The selected list of paths goes to $GIT_COMMON_DIR,
not the other way around in case a developer adds a new
worktree-specific file and it's accidentally promoted to be shared
across repositories (this includes unknown files added by third party
commands)

The list of known files that belong to $GIT_DIR are:

ADD_EDIT.patch BISECT_ANCESTORS_OK BISECT_EXPECTED_REV BISECT_LOG
BISECT_NAMES CHERRY_PICK_HEAD COMMIT_MSG FETCH_HEAD HEAD MERGE_HEAD
MERGE_MODE MERGE_RR NOTES_EDITMSG NOTES_MERGE_WORKTREE ORIG_HEAD
REVERT_HEAD SQUASH_MSG TAG_EDITMSG fast_import_crash_* logs/HEAD
next-index-* rebase-apply rebase-merge rsync-refs-* sequencer/*
shallow_*

Path mapping is NOT done for git_path_submodule(). Multi-checkouts are
not supported as submodules.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git.txt                  |  8 +++++++
 Documentation/gitrepository-layout.txt | 42 ++++++++++++++++++++++++++--------
 cache.h                                |  4 +++-
 environment.c                          | 28 +++++++++++++++++------
 path.c                                 | 34 +++++++++++++++++++++++++++
 t/t0060-path-utils.sh                  | 15 ++++++++++++
 6 files changed, 114 insertions(+), 17 deletions(-)

diff --git a/Documentation/git.txt b/Documentation/git.txt
index 7924209..749052f 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -788,6 +788,14 @@ Git so take care if using Cogito etc.
 	an explicit repository directory set via 'GIT_DIR' or on the
 	command line.
 
+'GIT_COMMON_DIR'::
+	If this variable is set to a path, non-worktree files that are
+	normally in $GIT_DIR will be taken from this path
+	instead. Worktree-specific files such as HEAD or index are
+	taken from $GIT_DIR. See linkgit:gitrepository-layout[5] for
+	details. This variable has lower precedence than other path
+	variables such as GIT_INDEX_FILE, GIT_OBJECT_DIRECTORY...
+
 Git Commits
 ~~~~~~~~~~~
 'GIT_AUTHOR_NAME'::
diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
index 17d2ea6..7629e38 100644
--- a/Documentation/gitrepository-layout.txt
+++ b/Documentation/gitrepository-layout.txt
@@ -46,6 +46,9 @@ of incomplete object store is not suitable to be published for
 use with dumb transports but otherwise is OK as long as
 `objects/info/alternates` points at the object stores it
 borrows from.
++
+This directory is ignored if $GIT_COMMON_DIR is set and
+"$GIT_COMMON_DIR/objects" will be used instead.
 
 objects/[0-9a-f][0-9a-f]::
 	A newly created object is stored in its own file.
@@ -92,7 +95,8 @@ refs::
 	References are stored in subdirectories of this
 	directory.  The 'git prune' command knows to preserve
 	objects reachable from refs found in this directory and
-	its subdirectories.
+	its subdirectories. This directory is ignored if $GIT_COMMON_DIR
+	is set and "$GIT_COMMON_DIR/refs" will be used instead.
 
 refs/heads/`name`::
 	records tip-of-the-tree commit objects of branch `name`
@@ -114,7 +118,8 @@ refs/replace/`<obj-sha1>`::
 packed-refs::
 	records the same information as refs/heads/, refs/tags/,
 	and friends record in a more efficient way.  See
-	linkgit:git-pack-refs[1].
+	linkgit:git-pack-refs[1]. This file is ignored if $GIT_COMMON_DIR
+	is set and "$GIT_COMMON_DIR/packed-refs" will be used instead.
 
 HEAD::
 	A symref (see glossary) to the `refs/heads/` namespace
@@ -133,6 +138,11 @@ being a symref to point at the current branch.  Such a state
 is often called 'detached HEAD.'  See linkgit:git-checkout[1]
 for details.
 
+config::
+	Repository specific configuration file. This file is ignored
+	$GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/config" will be
+	used instead.
+
 branches::
 	A slightly deprecated way to store shorthands to be used
 	to specify a URL to 'git fetch', 'git pull' and 'git push'.
@@ -140,7 +150,10 @@ branches::
 	'name' can be given to these commands in place of
 	'repository' argument.  See the REMOTES section in
 	linkgit:git-fetch[1] for details.  This mechanism is legacy
-	and not likely to be found in modern repositories.
+	and not likely to be found in modern repositories. This
+	directory is ignored if $GIT_COMMON_DIR is set and
+	"$GIT_COMMON_DIR/branches" will be used instead.
+
 
 hooks::
 	Hooks are customization scripts used by various Git
@@ -149,7 +162,9 @@ hooks::
 	default.  To enable, the `.sample` suffix has to be
 	removed from the filename by renaming.
 	Read linkgit:githooks[5] for more details about
-	each hook.
+	each hook. This directory is ignored if $GIT_COMMON_DIR is set
+	and "$GIT_COMMON_DIR/hooks" will be used instead.
+
 
 index::
 	The current index file for the repository.  It is
@@ -157,7 +172,8 @@ index::
 
 info::
 	Additional information about the repository is recorded
-	in this directory.
+	in this directory. This directory is ignored if $GIT_COMMON_DIR
+	is set and "$GIT_COMMON_DIR/index" will be used instead.
 
 info/refs::
 	This file helps dumb transports discover what refs are
@@ -197,12 +213,16 @@ remotes::
 	when interacting with remote repositories via 'git fetch',
 	'git pull' and 'git push' commands.  See the REMOTES section
 	in linkgit:git-fetch[1] for details.  This mechanism is legacy
-	and not likely to be found in modern repositories.
+	and not likely to be found in modern repositories. This
+	directory is ignored if $GIT_COMMON_DIR is set and
+	"$GIT_COMMON_DIR/remotes" will be used instead.
 
 logs::
 	Records of changes made to refs are stored in this
 	directory.  See linkgit:git-update-ref[1]
-	for more information.
+	for more information. This directory is ignored
+	$GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/logs" will be used
+	instead.
 
 logs/refs/heads/`name`::
 	Records all changes made to the branch tip named `name`.
@@ -213,10 +233,14 @@ logs/refs/tags/`name`::
 shallow::
 	This is similar to `info/grafts` but is internally used
 	and maintained by shallow clone mechanism.  See `--depth`
-	option to linkgit:git-clone[1] and linkgit:git-fetch[1].
+	option to linkgit:git-clone[1] and linkgit:git-fetch[1]. This
+	file is ignored if $GIT_COMMON_DIR is set and
+	"$GIT_COMMON_DIR/shallow" will be used instead.
 
 modules::
-	Contains the git-repositories of the submodules.
+	Contains the git-repositories of the submodules. This
+	directory is ignored if $GIT_COMMON_DIR is set and
+	"$GIT_COMMON_DIR/modules" will be used instead.
 
 SEE ALSO
 --------
diff --git a/cache.h b/cache.h
index 0128b9a..b606ee4 100644
--- a/cache.h
+++ b/cache.h
@@ -362,6 +362,7 @@ static inline enum object_type object_type(unsigned int mode)
 
 /* Double-check local_repo_env below if you add to this list. */
 #define GIT_DIR_ENVIRONMENT "GIT_DIR"
+#define GIT_COMMON_DIR_ENVIRONMENT "GIT_COMMON_DIR"
 #define GIT_NAMESPACE_ENVIRONMENT "GIT_NAMESPACE"
 #define GIT_WORK_TREE_ENVIRONMENT "GIT_WORK_TREE"
 #define GIT_PREFIX_ENVIRONMENT "GIT_PREFIX"
@@ -415,6 +416,7 @@ extern int is_inside_git_dir(void);
 extern char *git_work_tree_cfg;
 extern int is_inside_work_tree(void);
 extern const char *get_git_dir(void);
+extern const char *get_git_common_dir(void);
 extern int is_git_directory(const char *path);
 extern char *get_object_directory(void);
 extern char *get_index_file(void);
@@ -612,7 +614,7 @@ extern int fsync_object_files;
 extern int core_preload_index;
 extern int core_apply_sparse_checkout;
 extern int precomposed_unicode;
-extern int git_db_env, git_index_env, git_graft_env;
+extern int git_db_env, git_index_env, git_graft_env, git_common_dir_env;
 
 /*
  * The character that begins a commented line in user-editable file
diff --git a/environment.c b/environment.c
index fee12a6..6b74f68 100644
--- a/environment.c
+++ b/environment.c
@@ -81,9 +81,9 @@ static char *work_tree;
 static const char *namespace;
 static size_t namespace_len;
 
-static const char *git_dir;
+static const char *git_dir, *git_common_dir;
 static char *git_object_dir, *git_index_file, *git_graft_file;
-int git_db_env, git_index_env, git_graft_env;
+int git_db_env, git_index_env, git_graft_env, git_common_dir_env;
 
 /*
  * Repository-local GIT_* environment variables; see cache.h for details.
@@ -125,8 +125,8 @@ static char *expand_namespace(const char *raw_namespace)
 	return strbuf_detach(&buf, NULL);
 }
 
-static char *git_path_from_env(const char *envvar, const char *path,
-			       int *fromenv)
+static char *git_path_from_env(const char *envvar, const char *git_dir,
+			       const char *path, int *fromenv)
 {
 	const char *value = getenv(envvar);
 	if (!value) {
@@ -149,9 +149,18 @@ static void setup_git_env(void)
 		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
 	gitfile = read_gitfile(git_dir);
 	git_dir = xstrdup(gitfile ? gitfile : git_dir);
-	git_object_dir = git_path_from_env(DB_ENVIRONMENT, "objects", &git_db_env);
-	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, "index", &git_index_env);
-	git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, "info/grafts", &git_graft_env);
+	git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
+	if (git_common_dir) {
+		git_common_dir_env = 1;
+		git_common_dir = xstrdup(git_common_dir);
+	} else
+		git_common_dir = git_dir;
+	git_object_dir = git_path_from_env(DB_ENVIRONMENT, git_common_dir,
+					   "objects", &git_db_env);
+	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, git_dir,
+					   "index", &git_index_env);
+	git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, git_dir,
+					   "info/grafts", &git_graft_env);
 	if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
 		check_replace_refs = 0;
 	namespace = expand_namespace(getenv(GIT_NAMESPACE_ENVIRONMENT));
@@ -174,6 +183,11 @@ const char *get_git_dir(void)
 	return git_dir;
 }
 
+const char *get_git_common_dir(void)
+{
+	return git_common_dir;
+}
+
 const char *get_git_namespace(void)
 {
 	if (!namespace)
diff --git a/path.c b/path.c
index 3deb80c..8a6586c 100644
--- a/path.c
+++ b/path.c
@@ -90,6 +90,38 @@ static void replace_dir(struct strbuf *buf, int len, const char *newdir)
 		buf->buf[newlen] = '/';
 }
 
+static const char *common_list[] = {
+	"/branches", "/hooks", "/info", "/logs", "/lost-found", "/modules",
+	"/objects", "/refs", "/remotes", "/rr-cache", "/svn",
+	"config", "gc.pid", "packed-refs", "shallow",
+	NULL
+};
+
+static void update_common_dir(struct strbuf *buf, int git_dir_len)
+{
+	char *base = buf->buf + git_dir_len;
+	const char **p;
+
+	if (is_dir_file(base, "logs", "HEAD"))
+		return;	/* keep this in $GIT_DIR */
+	for (p = common_list; *p; p++) {
+		const char *path = *p;
+		int is_dir = 0;
+		if (*path == '/') {
+			path++;
+			is_dir = 1;
+		}
+		if (is_dir && dir_prefix(base, path)) {
+			replace_dir(buf, git_dir_len, get_git_common_dir());
+			return;
+		}
+		if (!is_dir && !strcmp(base, path)) {
+			replace_dir(buf, git_dir_len, get_git_common_dir());
+			return;
+		}
+	}
+}
+
 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 {
 	const char *base = buf->buf + git_dir_len;
@@ -101,6 +133,8 @@ static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 			      get_index_file(), strlen(get_index_file()));
 	else if (git_db_env && dir_prefix(base, "objects"))
 		replace_dir(buf, git_dir_len + 7, get_object_directory());
+	else if (git_common_dir_env)
+		update_common_dir(buf, git_dir_len);
 }
 
 static void do_git_path(struct strbuf *buf, const char *fmt, va_list args)
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 33d2818..2dabcef 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -262,5 +262,20 @@ test_expect_success 'setup fake objects directory foo' 'mkdir foo'
 test_git_path GIT_OBJECT_DIRECTORY=foo objects foo
 test_git_path GIT_OBJECT_DIRECTORY=foo objects/foo foo/foo
 test_git_path GIT_OBJECT_DIRECTORY=foo objects2 .git/objects2
+test_expect_success 'setup common repository' 'git --git-dir=bar init'
+test_git_path GIT_COMMON_DIR=bar index                    .git/index
+test_git_path GIT_COMMON_DIR=bar HEAD                     .git/HEAD
+test_git_path GIT_COMMON_DIR=bar logs/HEAD                .git/logs/HEAD
+test_git_path GIT_COMMON_DIR=bar objects                  bar/objects
+test_git_path GIT_COMMON_DIR=bar objects/bar              bar/objects/bar
+test_git_path GIT_COMMON_DIR=bar info/exclude             bar/info/exclude
+test_git_path GIT_COMMON_DIR=bar remotes/bar              bar/remotes/bar
+test_git_path GIT_COMMON_DIR=bar branches/bar             bar/branches/bar
+test_git_path GIT_COMMON_DIR=bar logs/refs/heads/master   bar/logs/refs/heads/master
+test_git_path GIT_COMMON_DIR=bar refs/heads/master        bar/refs/heads/master
+test_git_path GIT_COMMON_DIR=bar hooks/me                 bar/hooks/me
+test_git_path GIT_COMMON_DIR=bar config                   bar/config
+test_git_path GIT_COMMON_DIR=bar packed-refs              bar/packed-refs
+test_git_path GIT_COMMON_DIR=bar shallow                  bar/shallow
 
 test_done
-- 
1.9.1.346.ga2b5940

[PATCH v7 12/31] git-sh-setup.sh: use rev-parse --git-path to get $GIT_DIR/objects

[Nguyễn Thái Ngọc Duy]

If $GIT_COMMON_DIR is set, $GIT_OBJECT_DIRECTORY should be
$GIT_COMMON_DIR/objects, not $GIT_DIR/objects. Just let rev-parse
--git-path handle it.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 git-sh-setup.sh | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/git-sh-setup.sh b/git-sh-setup.sh
index 9447980..d3dbb2f 100644
--- a/git-sh-setup.sh
+++ b/git-sh-setup.sh
@@ -345,7 +345,7 @@ then
 		echo >&2 "Unable to determine absolute path of git directory"
 		exit 1
 	}
-	: ${GIT_OBJECT_DIRECTORY="$GIT_DIR/objects"}
+	: ${GIT_OBJECT_DIRECTORY="$(git rev-parse --git-path objects)"}
 fi
 
 peel_committish () {
-- 
1.9.1.346.ga2b5940

[PATCH v7 13/31] *.sh: avoid hardcoding $GIT_DIR/hooks/...

[Nguyễn Thái Ngọc Duy]

If $GIT_COMMON_DIR is set, it should be $GIT_COMMON_DIR/hooks/, not
$GIT_DIR/hooks/. Just let rev-parse --git-path handle it.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 git-am.sh                              | 22 +++++++++++-----------
 git-rebase--interactive.sh             |  6 +++---
 git-rebase--merge.sh                   |  6 ++----
 git-rebase.sh                          |  4 ++--
 templates/hooks--applypatch-msg.sample |  4 ++--
 templates/hooks--pre-applypatch.sample |  4 ++--
 6 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/git-am.sh b/git-am.sh
index ee61a77..66803d1 100755
--- a/git-am.sh
+++ b/git-am.sh
@@ -810,10 +810,10 @@ To restore the original branch and stop patching run \"\$cmdline --abort\"."
 		continue
 	fi
 
-	if test -x "$GIT_DIR"/hooks/applypatch-msg
+	hook="$(git rev-parse --git-path hooks/applypatch-msg)"
+	if test -x "$hook"
 	then
-		"$GIT_DIR"/hooks/applypatch-msg "$dotest/final-commit" ||
-		stop_here $this
+		"$hook" "$dotest/final-commit" || stop_here $this
 	fi
 
 	if test -f "$dotest/final-commit"
@@ -887,9 +887,10 @@ did you forget to use 'git add'?"
 		stop_here_user_resolve $this
 	fi
 
-	if test -x "$GIT_DIR"/hooks/pre-applypatch
+	hook="$(git rev-parse --git-path hooks/pre-applypatch)"
+	if test -x "$hook"
 	then
-		"$GIT_DIR"/hooks/pre-applypatch || stop_here $this
+		"$hook" || stop_here $this
 	fi
 
 	tree=$(git write-tree) &&
@@ -916,18 +917,17 @@ did you forget to use 'git add'?"
 		echo "$(cat "$dotest/original-commit") $commit" >> "$dotest/rewritten"
 	fi
 
-	if test -x "$GIT_DIR"/hooks/post-applypatch
-	then
-		"$GIT_DIR"/hooks/post-applypatch
-	fi
+	hook="$(git rev-parse --git-path hooks/post-applypatch)"
+	test -x "$hook" && "$hook"
 
 	go_next
 done
 
 if test -s "$dotest"/rewritten; then
     git notes copy --for-rewrite=rebase < "$dotest"/rewritten
-    if test -x "$GIT_DIR"/hooks/post-rewrite; then
-	"$GIT_DIR"/hooks/post-rewrite rebase < "$dotest"/rewritten
+    hook="$(git rev-parse --git-path hooks/post-rewrite)"
+    if test -x "$hook"; then
+	"$hook" rebase < "$dotest"/rewritten
     fi
 fi
 
diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
index 7e1eda0..e8995f9 100644
--- a/git-rebase--interactive.sh
+++ b/git-rebase--interactive.sh
@@ -642,9 +642,9 @@ do_next () {
 		git notes copy --for-rewrite=rebase < "$rewritten_list" ||
 		true # we don't care if this copying failed
 	} &&
-	if test -x "$GIT_DIR"/hooks/post-rewrite &&
-		test -s "$rewritten_list"; then
-		"$GIT_DIR"/hooks/post-rewrite rebase < "$rewritten_list"
+	hook="$(git rev-parse --git-path hooks/post-rewrite)"
+	if test -x "$hook" && test -s "$rewritten_list"; then
+		"$hook" rebase < "$rewritten_list"
 		true # we don't care if this hook failed
 	fi &&
 	warn "Successfully rebased and updated $head_name."
diff --git a/git-rebase--merge.sh b/git-rebase--merge.sh
index d3fb67d..2cc2a6d 100644
--- a/git-rebase--merge.sh
+++ b/git-rebase--merge.sh
@@ -94,10 +94,8 @@ finish_rb_merge () {
 	if test -s "$state_dir"/rewritten
 	then
 		git notes copy --for-rewrite=rebase <"$state_dir"/rewritten
-		if test -x "$GIT_DIR"/hooks/post-rewrite
-		then
-			"$GIT_DIR"/hooks/post-rewrite rebase <"$state_dir"/rewritten
-		fi
+		hook="$(git rev-parse --git-path hooks/post-rewrite)"
+		test -x "$hook" && "$hook" rebase <"$state_dir"/rewritten
 	fi
 	say All done.
 }
diff --git a/git-rebase.sh b/git-rebase.sh
index 06c810b..d60e710 100755
--- a/git-rebase.sh
+++ b/git-rebase.sh
@@ -201,9 +201,9 @@ run_specific_rebase () {
 
 run_pre_rebase_hook () {
 	if test -z "$ok_to_skip_pre_rebase" &&
-	   test -x "$GIT_DIR/hooks/pre-rebase"
+	   test -x "$(git rev-parse --git-path hooks/pre-rebase)"
 	then
-		"$GIT_DIR/hooks/pre-rebase" ${1+"$@"} ||
+		"$(git rev-parse --git-path hooks/pre-rebase)" ${1+"$@"} ||
 		die "$(gettext "The pre-rebase hook refused to rebase.")"
 	fi
 }
diff --git a/templates/hooks--applypatch-msg.sample b/templates/hooks--applypatch-msg.sample
index 8b2a2fe..a5d7b84 100755
--- a/templates/hooks--applypatch-msg.sample
+++ b/templates/hooks--applypatch-msg.sample
@@ -10,6 +10,6 @@
 # To enable this hook, rename this file to "applypatch-msg".
 
 . git-sh-setup
-test -x "$GIT_DIR/hooks/commit-msg" &&
-	exec "$GIT_DIR/hooks/commit-msg" ${1+"$@"}
+commitmsg="$(git rev-parse --git-path hooks/commit-msg)"
+test -x "$commitmsg" && exec "$commitmsg" ${1+"$@"}
 :
diff --git a/templates/hooks--pre-applypatch.sample b/templates/hooks--pre-applypatch.sample
index b1f187c..4142082 100755
--- a/templates/hooks--pre-applypatch.sample
+++ b/templates/hooks--pre-applypatch.sample
@@ -9,6 +9,6 @@
 # To enable this hook, rename this file to "pre-applypatch".
 
 . git-sh-setup
-test -x "$GIT_DIR/hooks/pre-commit" &&
-	exec "$GIT_DIR/hooks/pre-commit" ${1+"$@"}
+precommit="$(git rev-parse --git-path hooks/pre-commit)"
+test -x "$precommit" && exec "$precommit" ${1+"$@"}
 :
-- 
1.9.1.346.ga2b5940

[PATCH v7 14/31] git-stash: avoid hardcoding $GIT_DIR/logs/....

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 git-stash.sh | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/git-stash.sh b/git-stash.sh
index 393e1ec..41f8f6b 100755
--- a/git-stash.sh
+++ b/git-stash.sh
@@ -184,7 +184,7 @@ store_stash () {
 	fi
 
 	# Make sure the reflog for stash is kept.
-	: >>"$GIT_DIR/logs/$ref_stash"
+	: >>"$(git rev-parse --git-path logs/$ref_stash)"
 	git update-ref -m "$stash_msg" $ref_stash $w_commit
 	ret=$?
 	test $ret != 0 && test -z $quiet &&
@@ -259,7 +259,7 @@ save_stash () {
 		say "$(gettext "No local changes to save")"
 		exit 0
 	fi
-	test -f "$GIT_DIR/logs/$ref_stash" ||
+	test -f "$(git rev-parse --git-path logs/$ref_stash)" ||
 		clear_stash || die "$(gettext "Cannot initialize stash")"
 
 	create_stash "$stash_msg" $untracked
-- 
1.9.1.346.ga2b5940

[PATCH v7 15/31] setup.c: convert is_git_directory() to use strbuf

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 setup.c | 37 +++++++++++++++++++++----------------
 1 file changed, 21 insertions(+), 16 deletions(-)

diff --git a/setup.c b/setup.c
index 0a22f8b..425fd79 100644
--- a/setup.c
+++ b/setup.c
@@ -238,31 +238,36 @@ void verify_non_filename(const char *prefix, const char *arg)
  */
 int is_git_directory(const char *suspect)
 {
-	char path[PATH_MAX];
-	size_t len = strlen(suspect);
+	struct strbuf path = STRBUF_INIT;
+	int ret = 0;
+	size_t len;
 
-	if (PATH_MAX <= len + strlen("/objects"))
-		die("Too long path: %.*s", 60, suspect);
-	strcpy(path, suspect);
+	strbuf_addstr(&path, suspect);
+	len = path.len;
 	if (getenv(DB_ENVIRONMENT)) {
 		if (access(getenv(DB_ENVIRONMENT), X_OK))
-			return 0;
+			goto done;
 	}
 	else {
-		strcpy(path + len, "/objects");
-		if (access(path, X_OK))
-			return 0;
+		strbuf_addstr(&path, "/objects");
+		if (access(path.buf, X_OK))
+			goto done;
 	}
 
-	strcpy(path + len, "/refs");
-	if (access(path, X_OK))
-		return 0;
+	strbuf_setlen(&path, len);
+	strbuf_addstr(&path, "/refs");
+	if (access(path.buf, X_OK))
+		goto done;
 
-	strcpy(path + len, "/HEAD");
-	if (validate_headref(path))
-		return 0;
+	strbuf_setlen(&path, len);
+	strbuf_addstr(&path, "/HEAD");
+	if (validate_headref(path.buf))
+		goto done;
 
-	return 1;
+	ret = 1;
+done:
+	strbuf_release(&path);
+	return ret;
 }
 
 int is_inside_git_dir(void)
-- 
1.9.1.346.ga2b5940

[PATCH v7 16/31] setup.c: detect $GIT_COMMON_DIR in is_git_directory()

[Nguyễn Thái Ngọc Duy]

If the file "$GIT_DIR/commondir" exists, it contains the value of
$GIT_COMMON_DIR.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/gitrepository-layout.txt |  7 ++++++
 setup.c                                | 43 +++++++++++++++++++++++++++++-----
 2 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
index 7629e38..0f341fc 100644
--- a/Documentation/gitrepository-layout.txt
+++ b/Documentation/gitrepository-layout.txt
@@ -237,6 +237,13 @@ shallow::
 	file is ignored if $GIT_COMMON_DIR is set and
 	"$GIT_COMMON_DIR/shallow" will be used instead.
 
+commondir::
+	If this file exists, $GIT_COMMON_DIR (see linkgit:git[1]) will
+	be set to the path specified in this file if it is not
+	explicitly set. If the specified path is relative, it is
+	relative to $GIT_DIR. The repository with commondir is
+	incomplete without the repository pointed by "commondir".
+
 modules::
 	Contains the git-repositories of the submodules. This
 	directory is ignored if $GIT_COMMON_DIR is set and
diff --git a/setup.c b/setup.c
index 425fd79..176d505 100644
--- a/setup.c
+++ b/setup.c
@@ -224,6 +224,33 @@ void verify_non_filename(const char *prefix, const char *arg)
 	    "'git <command> [<revision>...] -- [<file>...]'", arg);
 }
 
+static void get_common_dir(struct strbuf *sb, const char *gitdir)
+{
+	struct strbuf data = STRBUF_INIT;
+	struct strbuf path = STRBUF_INIT;
+	const char *git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
+	if (git_common_dir) {
+		strbuf_addstr(sb, git_common_dir);
+		return;
+	}
+	strbuf_addf(&path, "%s/commondir", gitdir);
+	if (file_exists(path.buf)) {
+		if (strbuf_read_file(&data, path.buf, 0) <= 0)
+			die_errno(_("failed to read %s"), path.buf);
+		while (data.len && (data.buf[data.len - 1] == '\n' ||
+				    data.buf[data.len - 1] == '\r'))
+			data.len--;
+		data.buf[data.len] = '\0';
+		strbuf_reset(&path);
+		if (!is_absolute_path(data.buf))
+			strbuf_addf(&path, "%s/", gitdir);
+		strbuf_addbuf(&path, &data);
+		strbuf_addstr(sb, real_path(path.buf));
+	} else
+		strbuf_addstr(sb, gitdir);
+	strbuf_release(&data);
+	strbuf_release(&path);
+}
 
 /*
  * Test if it looks like we're at a git directory.
@@ -242,13 +269,22 @@ int is_git_directory(const char *suspect)
 	int ret = 0;
 	size_t len;
 
-	strbuf_addstr(&path, suspect);
+	/* Check worktree-related signatures */
+	strbuf_addf(&path, "%s/HEAD", suspect);
+	if (validate_headref(path.buf))
+		goto done;
+
+	strbuf_reset(&path);
+	get_common_dir(&path, suspect);
 	len = path.len;
+
+	/* Check non-worktree-related signatures */
 	if (getenv(DB_ENVIRONMENT)) {
 		if (access(getenv(DB_ENVIRONMENT), X_OK))
 			goto done;
 	}
 	else {
+		strbuf_setlen(&path, len);
 		strbuf_addstr(&path, "/objects");
 		if (access(path.buf, X_OK))
 			goto done;
@@ -259,11 +295,6 @@ int is_git_directory(const char *suspect)
 	if (access(path.buf, X_OK))
 		goto done;
 
-	strbuf_setlen(&path, len);
-	strbuf_addstr(&path, "/HEAD");
-	if (validate_headref(path.buf))
-		goto done;
-
 	ret = 1;
 done:
 	strbuf_release(&path);
-- 
1.9.1.346.ga2b5940

[PATCH v7 17/31] setup.c: convert check_repository_format_gently to use strbuf

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 setup.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/setup.c b/setup.c
index 176d505..a17389f 100644
--- a/setup.c
+++ b/setup.c
@@ -342,7 +342,9 @@ void setup_work_tree(void)
 
 static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 {
-	char repo_config[PATH_MAX+1];
+	struct strbuf sb = STRBUF_INIT;
+	const char *repo_config;
+	int ret = 0;
 
 	/*
 	 * git_config() can't be used here because it calls git_pathdup()
@@ -353,7 +355,8 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 	 * Use a gentler version of git_config() to check if this repo
 	 * is a good one.
 	 */
-	snprintf(repo_config, PATH_MAX, "%s/config", gitdir);
+	strbuf_addf(&sb, "%s/config", gitdir);
+	repo_config = sb.buf;
 	git_config_early(check_repository_format_version, NULL, repo_config);
 	if (GIT_REPO_VERSION < repository_format_version) {
 		if (!nongit_ok)
@@ -363,9 +366,10 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 			GIT_REPO_VERSION, repository_format_version);
 		warning("Please upgrade Git");
 		*nongit_ok = -1;
-		return -1;
+		ret = -1;
 	}
-	return 0;
+	strbuf_release(&sb);
+	return ret;
 }
 
 /*
-- 
1.9.1.346.ga2b5940

[PATCH v7 18/31] setup.c: detect $GIT_COMMON_DIR check_repository_format_gently()

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 setup.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/setup.c b/setup.c
index a17389f..79f79f2 100644
--- a/setup.c
+++ b/setup.c
@@ -346,6 +346,10 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 	const char *repo_config;
 	int ret = 0;
 
+	get_common_dir(&sb, gitdir);
+	strbuf_addstr(&sb, "/config");
+	repo_config = sb.buf;
+
 	/*
 	 * git_config() can't be used here because it calls git_pathdup()
 	 * to get $GIT_CONFIG/config. That call will make setup_git_env()
@@ -355,8 +359,6 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 	 * Use a gentler version of git_config() to check if this repo
 	 * is a good one.
 	 */
-	strbuf_addf(&sb, "%s/config", gitdir);
-	repo_config = sb.buf;
 	git_config_early(check_repository_format_version, NULL, repo_config);
 	if (GIT_REPO_VERSION < repository_format_version) {
 		if (!nongit_ok)
-- 
1.9.1.346.ga2b5940

[PATCH v7 19/31] setup.c: support multi-checkout repo setup

[Nguyễn Thái Ngọc Duy]

The repo setup procedure is updated to detect $GIT_DIR/commondir and
set $GIT_COMMON_DIR properly.

The core.worktree is ignored when $GIT_COMMON_DIR is set. This is
because the config file is shared in multi-checkout setup, but
checkout directories _are_ different. Making core.worktree effective
in all checkouts mean it's back to a single checkout.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/config.txt        |  2 ++
 Documentation/git-rev-parse.txt |  3 ++
 builtin/rev-parse.c             |  4 +++
 cache.h                         |  1 +
 environment.c                   |  8 ++---
 setup.c                         | 33 +++++++++++++-----
 t/t1501-worktree.sh             | 76 +++++++++++++++++++++++++++++++++++++++++
 t/t1510-repo-setup.sh           |  1 +
 trace.c                         |  1 +
 9 files changed, 115 insertions(+), 14 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 1d718bd..286e539 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -380,6 +380,8 @@ false), while all other repositories are assumed to be bare (bare
 
 core.worktree::
 	Set the path to the root of the working tree.
+	If GIT_COMMON_DIR environment variable is set, core.worktree
+	is ignored and not used for determining the root of working tree.
 	This can be overridden by the GIT_WORK_TREE environment
 	variable and the '--work-tree' command-line option.
 	The value can be an absolute path or relative to the path to
diff --git a/Documentation/git-rev-parse.txt b/Documentation/git-rev-parse.txt
index 9465399..f1867d3 100644
--- a/Documentation/git-rev-parse.txt
+++ b/Documentation/git-rev-parse.txt
@@ -215,6 +215,9 @@ If `$GIT_DIR` is not defined and the current directory
 is not detected to lie in a Git repository or work tree
 print a message to stderr and exit with nonzero status.
 
+--git-common-dir::
+	Show `$GIT_COMMON_DIR` if defined, else `$GIT_DIR`.
+
 --is-inside-git-dir::
 	When the current working directory is below the repository
 	directory print "true", otherwise "false".
diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 7606d43..29475c5 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -757,6 +757,10 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				printf("%s%s.git\n", cwd, len && cwd[len-1] != '/' ? "/" : "");
 				continue;
 			}
+			if (!strcmp(arg, "--git-common-dir")) {
+				puts(get_git_common_dir());
+				continue;
+			}
 			if (!strcmp(arg, "--resolve-git-dir")) {
 				const char *gitdir = argv[++i];
 				if (!gitdir)
diff --git a/cache.h b/cache.h
index b606ee4..e3ff7dc 100644
--- a/cache.h
+++ b/cache.h
@@ -422,6 +422,7 @@ extern char *get_object_directory(void);
 extern char *get_index_file(void);
 extern char *get_graft_file(void);
 extern int set_git_dir(const char *path);
+extern int get_common_dir(struct strbuf *sb, const char *gitdir);
 extern const char *get_git_namespace(void);
 extern const char *strip_namespace(const char *namespaced_ref);
 extern const char *get_git_work_tree(void);
diff --git a/environment.c b/environment.c
index 6b74f68..50ed40a 100644
--- a/environment.c
+++ b/environment.c
@@ -141,6 +141,7 @@ static char *git_path_from_env(const char *envvar, const char *git_dir,
 
 static void setup_git_env(void)
 {
+	struct strbuf sb = STRBUF_INIT;
 	const char *gitfile;
 	const char *shallow_file;
 
@@ -149,12 +150,9 @@ static void setup_git_env(void)
 		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
 	gitfile = read_gitfile(git_dir);
 	git_dir = xstrdup(gitfile ? gitfile : git_dir);
-	git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
-	if (git_common_dir) {
+	if (get_common_dir(&sb, git_dir))
 		git_common_dir_env = 1;
-		git_common_dir = xstrdup(git_common_dir);
-	} else
-		git_common_dir = git_dir;
+	git_common_dir = strbuf_detach(&sb, NULL);
 	git_object_dir = git_path_from_env(DB_ENVIRONMENT, git_common_dir,
 					   "objects", &git_db_env);
 	git_index_file = git_path_from_env(INDEX_ENVIRONMENT, git_dir,
diff --git a/setup.c b/setup.c
index 79f79f2..8f90bc3 100644
--- a/setup.c
+++ b/setup.c
@@ -224,14 +224,15 @@ void verify_non_filename(const char *prefix, const char *arg)
 	    "'git <command> [<revision>...] -- [<file>...]'", arg);
 }
 
-static void get_common_dir(struct strbuf *sb, const char *gitdir)
+int get_common_dir(struct strbuf *sb, const char *gitdir)
 {
 	struct strbuf data = STRBUF_INIT;
 	struct strbuf path = STRBUF_INIT;
 	const char *git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
+	int ret = 0;
 	if (git_common_dir) {
 		strbuf_addstr(sb, git_common_dir);
-		return;
+		return 1;
 	}
 	strbuf_addf(&path, "%s/commondir", gitdir);
 	if (file_exists(path.buf)) {
@@ -246,10 +247,12 @@ static void get_common_dir(struct strbuf *sb, const char *gitdir)
 			strbuf_addf(&path, "%s/", gitdir);
 		strbuf_addbuf(&path, &data);
 		strbuf_addstr(sb, real_path(path.buf));
+		ret = 1;
 	} else
 		strbuf_addstr(sb, gitdir);
 	strbuf_release(&data);
 	strbuf_release(&path);
+	return ret;
 }
 
 /*
@@ -340,13 +343,26 @@ void setup_work_tree(void)
 	initialized = 1;
 }
 
+static int check_repo_format(const char *var, const char *value, void *cb)
+{
+	if (strcmp(var, "core.repositoryformatversion") == 0)
+		repository_format_version = git_config_int(var, value);
+	else if (strcmp(var, "core.sharedrepository") == 0)
+		shared_repository = git_config_perm(var, value);
+	return 0;
+}
+
 static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 {
 	struct strbuf sb = STRBUF_INIT;
 	const char *repo_config;
+	config_fn_t fn;
 	int ret = 0;
 
-	get_common_dir(&sb, gitdir);
+	if (get_common_dir(&sb, gitdir))
+		fn = check_repo_format;
+	else
+		fn = check_repository_format_version;
 	strbuf_addstr(&sb, "/config");
 	repo_config = sb.buf;
 
@@ -359,7 +375,7 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 	 * Use a gentler version of git_config() to check if this repo
 	 * is a good one.
 	 */
-	git_config_early(check_repository_format_version, NULL, repo_config);
+	git_config_early(fn, NULL, repo_config);
 	if (GIT_REPO_VERSION < repository_format_version) {
 		if (!nongit_ok)
 			die ("Expected git repo version <= %d, found %d",
@@ -831,11 +847,10 @@ int git_config_perm(const char *var, const char *value)
 
 int check_repository_format_version(const char *var, const char *value, void *cb)
 {
-	if (strcmp(var, "core.repositoryformatversion") == 0)
-		repository_format_version = git_config_int(var, value);
-	else if (strcmp(var, "core.sharedrepository") == 0)
-		shared_repository = git_config_perm(var, value);
-	else if (strcmp(var, "core.bare") == 0) {
+	int ret = check_repo_format(var, value, cb);
+	if (ret)
+		return ret;
+	if (strcmp(var, "core.bare") == 0) {
 		is_bare_repository_cfg = git_config_bool(var, value);
 		if (is_bare_repository_cfg == 1)
 			inside_work_tree = -1;
diff --git a/t/t1501-worktree.sh b/t/t1501-worktree.sh
index 8f36aa9..e6ac7a4 100755
--- a/t/t1501-worktree.sh
+++ b/t/t1501-worktree.sh
@@ -346,4 +346,80 @@ test_expect_success 'relative $GIT_WORK_TREE and git subprocesses' '
 	test_cmp expected actual
 '
 
+test_expect_success 'Multi-worktree setup' '
+	mkdir work &&
+	mkdir -p repo.git/repos/foo &&
+	cp repo.git/HEAD repo.git/index repo.git/repos/foo &&
+	sane_unset GIT_DIR GIT_CONFIG GIT_WORK_TREE
+'
+
+test_expect_success 'GIT_DIR set (1)' '
+	echo "gitdir: repo.git/repos/foo" >gitfile &&
+	echo ../.. >repo.git/repos/foo/commondir &&
+	(
+		cd work &&
+		GIT_DIR=../gitfile git rev-parse --git-common-dir >actual &&
+		test-path-utils real_path "$TRASH_DIRECTORY/repo.git" >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'GIT_DIR set (2)' '
+	echo "gitdir: repo.git/repos/foo" >gitfile &&
+	echo "$TRASH_DIRECTORY/repo.git" >repo.git/repos/foo/commondir &&
+	(
+		cd work &&
+		GIT_DIR=../gitfile git rev-parse --git-common-dir >actual &&
+		test-path-utils real_path "$TRASH_DIRECTORY/repo.git" >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'Auto discovery' '
+	echo "gitdir: repo.git/repos/foo" >.git &&
+	echo ../.. >repo.git/repos/foo/commondir &&
+	(
+		cd work &&
+		git rev-parse --git-common-dir >actual &&
+		test-path-utils real_path "$TRASH_DIRECTORY/repo.git" >expect &&
+		test_cmp expect actual &&
+		echo haha >data1 &&
+		git add data1 &&
+		git ls-files --full-name :/ | grep data1 >actual &&
+		echo work/data1 >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success '$GIT_DIR/common overrides core.worktree' '
+	mkdir elsewhere &&
+	git --git-dir=repo.git config core.worktree "$TRASH_DIRECTORY/elsewhere" &&
+	echo "gitdir: repo.git/repos/foo" >.git &&
+	echo ../.. >repo.git/repos/foo/commondir &&
+	(
+		cd work &&
+		git rev-parse --git-common-dir >actual &&
+		test-path-utils real_path "$TRASH_DIRECTORY/repo.git" >expect &&
+		test_cmp expect actual &&
+		echo haha >data2 &&
+		git add data2 &&
+		git ls-files --full-name :/ | grep data2 >actual &&
+		echo work/data2 >expect &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success '$GIT_WORK_TREE overrides $GIT_DIR/common' '
+	echo "gitdir: repo.git/repos/foo" >.git &&
+	echo ../.. >repo.git/repos/foo/commondir &&
+	(
+		cd work &&
+		echo haha >data3 &&
+		git --git-dir=../.git --work-tree=. add data3 &&
+		git ls-files --full-name -- :/ | grep data3 >actual &&
+		echo data3 >expect &&
+		test_cmp expect actual
+	)
+'
+
 test_done
diff --git a/t/t1510-repo-setup.sh b/t/t1510-repo-setup.sh
index e1b2a99..33c1a58 100755
--- a/t/t1510-repo-setup.sh
+++ b/t/t1510-repo-setup.sh
@@ -106,6 +106,7 @@ setup_env () {
 expect () {
 	cat >"$1/expected" <<-EOF
 	setup: git_dir: $2
+	setup: git_common_dir: $2
 	setup: worktree: $3
 	setup: cwd: $4
 	setup: prefix: $5
diff --git a/trace.c b/trace.c
index 08180a9..a594761 100644
--- a/trace.c
+++ b/trace.c
@@ -173,6 +173,7 @@ void trace_repo_setup(const char *prefix)
 		prefix = "(null)";
 
 	trace_printf_key(key, "setup: git_dir: %s\n", quote_crnl(get_git_dir()));
+	trace_printf_key(key, "setup: git_common_dir: %s\n", quote_crnl(get_git_common_dir()));
 	trace_printf_key(key, "setup: worktree: %s\n", quote_crnl(git_work_tree));
 	trace_printf_key(key, "setup: cwd: %s\n", quote_crnl(cwd));
 	trace_printf_key(key, "setup: prefix: %s\n", quote_crnl(prefix));
-- 
1.9.1.346.ga2b5940

[PATCH v7 20/31] wrapper.c: wrapper to open a file, fprintf then close

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 cache.h   |  2 ++
 wrapper.c | 31 +++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/cache.h b/cache.h
index e3ff7dc..bf4d15e 100644
--- a/cache.h
+++ b/cache.h
@@ -1359,6 +1359,8 @@ static inline ssize_t write_str_in_full(int fd, const char *str)
 {
 	return write_in_full(fd, str, strlen(str));
 }
+__attribute__((format (printf,3,4)))
+extern int write_file(const char *path, int fatal, const char *fmt, ...);
 
 /* pager.c */
 extern void setup_pager(void);
diff --git a/wrapper.c b/wrapper.c
index bc1bfb8..9d7b9ac 100644
--- a/wrapper.c
+++ b/wrapper.c
@@ -493,3 +493,34 @@ struct passwd *xgetpwuid_self(void)
 		    errno ? strerror(errno) : _("no such user"));
 	return pw;
 }
+
+int write_file(const char *path, int fatal, const char *fmt, ...)
+{
+	struct strbuf sb = STRBUF_INIT;
+	va_list params;
+	int fd = open(path, O_RDWR | O_CREAT | O_TRUNC, 0666);
+	if (fd < 0) {
+		if (fatal)
+			die_errno(_("could not open %s for writing"), path);
+		return -1;
+	}
+	va_start(params, fmt);
+	strbuf_vaddf(&sb, fmt, params);
+	va_end(params);
+	if (write_in_full(fd, sb.buf, sb.len) != sb.len) {
+		int err = errno;
+		close(fd);
+		strbuf_release(&sb);
+		errno = err;
+		if (fatal)
+			die_errno(_("could not write to %s"), path);
+		return -1;
+	}
+	strbuf_release(&sb);
+	if (close(fd)) {
+		if (fatal)
+			die_errno(_("could not close %s"), path);
+		return -1;
+	}
+	return 0;
+}
-- 
1.9.1.346.ga2b5940

[PATCH v7 21/31] use new wrapper write_file() for simple file writing

[Nguyễn Thái Ngọc Duy]

This fixes common problems in these code about error handling,
forgetting to close the file handle after fprintf() fails, or not
printing out the error string..

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/branch.c  |  4 +---
 builtin/init-db.c |  7 +------
 daemon.c          | 11 +----------
 submodule.c       |  9 ++-------
 transport.c       |  8 +++-----
 5 files changed, 8 insertions(+), 31 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index 0591b22..e4265a1 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -754,7 +754,6 @@ static const char edit_description[] = "BRANCH_DESCRIPTION";
 
 static int edit_branch_description(const char *branch_name)
 {
-	FILE *fp;
 	int status;
 	struct strbuf buf = STRBUF_INIT;
 	struct strbuf name = STRBUF_INIT;
@@ -767,8 +766,7 @@ static int edit_branch_description(const char *branch_name)
 		    "  %s\n"
 		    "Lines starting with '%c' will be stripped.\n",
 		    branch_name, comment_line_char);
-	fp = fopen(git_path(edit_description), "w");
-	if ((fwrite(buf.buf, 1, buf.len, fp) < buf.len) || fclose(fp)) {
+	if (write_file(git_path(edit_description), 0, "%s", buf.buf)) {
 		strbuf_release(&buf);
 		return error(_("could not write branch description template: %s"),
 			     strerror(errno));
diff --git a/builtin/init-db.c b/builtin/init-db.c
index 56f85e2..ce8416a 100644
--- a/builtin/init-db.c
+++ b/builtin/init-db.c
@@ -342,7 +342,6 @@ int set_git_dir_init(const char *git_dir, const char *real_git_dir,
 static void separate_git_dir(const char *git_dir)
 {
 	struct stat st;
-	FILE *fp;
 
 	if (!stat(git_link, &st)) {
 		const char *src;
@@ -358,11 +357,7 @@ static void separate_git_dir(const char *git_dir)
 			die_errno(_("unable to move %s to %s"), src, git_dir);
 	}
 
-	fp = fopen(git_link, "w");
-	if (!fp)
-		die(_("Could not create git link %s"), git_link);
-	fprintf(fp, "gitdir: %s\n", git_dir);
-	fclose(fp);
+	write_file(git_link, 1, "gitdir: %s\n", git_dir);
 }
 
 int init_db(const char *template_dir, unsigned int flags)
diff --git a/daemon.c b/daemon.c
index 1eb6631..dd638a9 100644
--- a/daemon.c
+++ b/daemon.c
@@ -1094,15 +1094,6 @@ static struct credentials *prepare_credentials(const char *user_name,
 }
 #endif
 
-static void store_pid(const char *path)
-{
-	FILE *f = fopen(path, "w");
-	if (!f)
-		die_errno("cannot open pid file '%s'", path);
-	if (fprintf(f, "%"PRIuMAX"\n", (uintmax_t) getpid()) < 0 || fclose(f) != 0)
-		die_errno("failed to write pid file '%s'", path);
-}
-
 static int serve(struct string_list *listen_addr, int listen_port,
     struct credentials *cred)
 {
@@ -1313,7 +1304,7 @@ int main(int argc, char **argv)
 		sanitize_stdfds();
 
 	if (pid_file)
-		store_pid(pid_file);
+		write_file(pid_file, 1, "%"PRIuMAX"\n", (uintmax_t) getpid());
 
 	/* prepare argv for serving-processes */
 	cld_argv = xmalloc(sizeof (char *) * (argc + 2));
diff --git a/submodule.c b/submodule.c
index b80ecac..b7b6059 100644
--- a/submodule.c
+++ b/submodule.c
@@ -1112,16 +1112,11 @@ void connect_work_tree_and_git_dir(const char *work_tree, const char *git_dir)
 	struct strbuf file_name = STRBUF_INIT;
 	struct strbuf rel_path = STRBUF_INIT;
 	const char *real_work_tree = xstrdup(real_path(work_tree));
-	FILE *fp;
 
 	/* Update gitfile */
 	strbuf_addf(&file_name, "%s/.git", work_tree);
-	fp = fopen(file_name.buf, "w");
-	if (!fp)
-		die(_("Could not create git link %s"), file_name.buf);
-	fprintf(fp, "gitdir: %s\n", relative_path(git_dir, real_work_tree,
-						  &rel_path));
-	fclose(fp);
+	write_file(file_name.buf, 1, "gitdir: %s\n",
+		   relative_path(git_dir, real_work_tree, &rel_path));
 
 	/* Update core.worktree setting */
 	strbuf_reset(&file_name);
diff --git a/transport.c b/transport.c
index 59c9727..1b779bb 100644
--- a/transport.c
+++ b/transport.c
@@ -296,7 +296,6 @@ static int write_one_ref(const char *name, const unsigned char *sha1,
 {
 	struct strbuf *buf = data;
 	int len = buf->len;
-	FILE *f;
 
 	/* when called via for_each_ref(), flags is non-zero */
 	if (flags && !starts_with(name, "refs/heads/") &&
@@ -305,10 +304,9 @@ static int write_one_ref(const char *name, const unsigned char *sha1,
 
 	strbuf_addstr(buf, name);
 	if (safe_create_leading_directories(buf->buf) ||
-			!(f = fopen(buf->buf, "w")) ||
-			fprintf(f, "%s\n", sha1_to_hex(sha1)) < 0 ||
-			fclose(f))
-		return error("problems writing temporary file %s", buf->buf);
+	    write_file(buf->buf, 0, "%s\n", sha1_to_hex(sha1)))
+		return error("problems writing temporary file %s: %s",
+			     buf->buf, strerror(errno));
 	strbuf_setlen(buf, len);
 	return 0;
 }
-- 
1.9.1.346.ga2b5940

[PATCH v7 22/31] checkout: support checking out into a new working directory

[Nguyễn Thái Ngọc Duy]

"git checkout --to" sets up a new working directory with a .git file
pointing to $GIT_DIR/repos/<id>. It then executes "git checkout" again
on the new worktree with the same arguments except "--to" is taken
out. The second checkout execution, which is not contaminated with any
info from the current repository, will actually check out and
everything that normal "git checkout" does.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git-checkout.txt         | 34 +++++++++++++
 Documentation/git.txt                  |  3 +-
 Documentation/gitrepository-layout.txt |  7 +++
 builtin/checkout.c                     | 93 +++++++++++++++++++++++++++++++++-
 path.c                                 |  2 +-
 t/t2025-checkout-to.sh (new +x)        | 48 ++++++++++++++++++
 6 files changed, 183 insertions(+), 4 deletions(-)
 create mode 100755 t/t2025-checkout-to.sh

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 33ad2ad..fcf73b2 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -225,6 +225,13 @@ This means that you can use `git checkout -p` to selectively discard
 edits from your current working tree. See the ``Interactive Mode''
 section of linkgit:git-add[1] to learn how to operate the `--patch` mode.
 
+--to=<path>::
+	Check out a new branch in a separate working directory at
+	`<path>`. A new working directory is linked to the current
+	repository, sharing everything except working directory
+	specific files such as HEAD, index... See "MULTIPLE CHECKOUT
+	MODE" section for more information.
+
 <branch>::
 	Branch to checkout; if it refers to a branch (i.e., a name that,
 	when prepended with "refs/heads/", is a valid ref), then that
@@ -388,6 +395,33 @@ $ git reflog -2 HEAD # or
 $ git log -g -2 HEAD
 ------------
 
+MULTIPLE CHECKOUT MODE
+-------------------------------
+Normally a working directory is attached to repository. When "git
+checkout --to" is used, a new working directory is attached to the
+current repository. This new working directory is called "linked
+checkout" as compared to the "main checkout" prepared by "git init" or
+"git clone". A repository has one main checkout and zero or more
+linked checkouts.
+
+All checkouts share the same repository. Linked checkouts see the
+repository a bit different from the main checkout. When the checkout
+"new" reads the path $GIT_DIR/HEAD for example, the actual path
+returned could be $GIT_DIR/repos/new/HEAD. This ensures checkouts
+won't step on each other.
+
+Each linked checkout has a private space in $GIT_DIR/repos, usually
+named after the base name of the working directory with a number added
+to make it unique. The linked checkout's $GIT_DIR points to this
+private space while $GIT_COMMON_DIR points to the main checkout's
+$GIT_DIR. These settings are done by "git checkout --to".
+
+Because in this mode $GIT_DIR becomes a lightweight virtual file
+system where a path could be rewritten to some place else, accessing
+$GIT_DIR from scripts should use `git rev-parse --git-path` to resolve
+a path instead of using it directly unless the path is known to be
+private to the working directory.
+
 EXAMPLES
 --------
 
diff --git a/Documentation/git.txt b/Documentation/git.txt
index 749052f..c0a4940 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -792,7 +792,8 @@ Git so take care if using Cogito etc.
 	If this variable is set to a path, non-worktree files that are
 	normally in $GIT_DIR will be taken from this path
 	instead. Worktree-specific files such as HEAD or index are
-	taken from $GIT_DIR. See linkgit:gitrepository-layout[5] for
+	taken from $GIT_DIR. See linkgit:gitrepository-layout[5] and
+	the section 'MULTIPLE CHECKOUT MODE' in linkgit:checkout[1]
 	details. This variable has lower precedence than other path
 	variables such as GIT_INDEX_FILE, GIT_OBJECT_DIRECTORY...
 
diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
index 0f341fc..543d874 100644
--- a/Documentation/gitrepository-layout.txt
+++ b/Documentation/gitrepository-layout.txt
@@ -249,6 +249,13 @@ modules::
 	directory is ignored if $GIT_COMMON_DIR is set and
 	"$GIT_COMMON_DIR/modules" will be used instead.
 
+repos::
+	Contains worktree specific information of linked
+	checkouts. Each subdirectory contains the worktree-related
+	part of a linked checkout. This directory is ignored
+	$GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/repos" will be
+	used instead.
+
 SEE ALSO
 --------
 linkgit:git-init[1],
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 8023987..81adb74 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -48,6 +48,10 @@ struct checkout_opts {
 	const char *prefix;
 	struct pathspec pathspec;
 	struct tree *source_tree;
+
+	const char *new_worktree;
+	const char **saved_argv;
+	int new_worktree_mode;
 };
 
 static int post_checkout_hook(struct commit *old, struct commit *new,
@@ -250,6 +254,9 @@ static int checkout_paths(const struct checkout_opts *opts,
 		die(_("Cannot update paths and switch to branch '%s' at the same time."),
 		    opts->new_branch);
 
+	if (opts->new_worktree)
+		die(_("'%s' cannot be used with updating paths"), "--to");
+
 	if (opts->patch_mode)
 		return run_add_interactive(revision, "--patch=checkout",
 					   &opts->pathspec);
@@ -485,7 +492,7 @@ static int merge_working_tree(const struct checkout_opts *opts,
 			topts.dir->flags |= DIR_SHOW_IGNORED;
 			setup_standard_excludes(topts.dir);
 		}
-		tree = parse_tree_indirect(old->commit ?
+		tree = parse_tree_indirect(old->commit && !opts->new_worktree_mode ?
 					   old->commit->object.sha1 :
 					   EMPTY_TREE_SHA1_BIN);
 		init_tree_desc(&trees[0], tree->buffer, tree->size);
@@ -796,7 +803,8 @@ static int switch_branches(const struct checkout_opts *opts,
 		return ret;
 	}
 
-	if (!opts->quiet && !old.path && old.commit && new->commit != old.commit)
+	if (!opts->quiet && !old.path && old.commit &&
+	    new->commit != old.commit && !opts->new_worktree_mode)
 		orphaned_commit_warning(old.commit, new->commit);
 
 	update_refs_for_switch(opts, &old, new);
@@ -806,6 +814,74 @@ static int switch_branches(const struct checkout_opts *opts,
 	return ret || writeout_error;
 }
 
+static int prepare_linked_checkout(const struct checkout_opts *opts,
+				   struct branch_info *new)
+{
+	struct strbuf sb_git = STRBUF_INIT, sb_repo = STRBUF_INIT;
+	struct strbuf sb = STRBUF_INIT;
+	const char *path = opts->new_worktree, *name;
+	struct stat st;
+	struct child_process cp;
+	int counter = 0, len;
+
+	if (!new->commit)
+		die(_("no branch specified"));
+
+	len = strlen(path);
+	while (len && is_dir_sep(path[len - 1]))
+		len--;
+
+	for (name = path + len - 1; name > path; name--)
+		if (is_dir_sep(*name)) {
+			name++;
+			break;
+		}
+	strbuf_addstr(&sb_repo,
+		      git_path("repos/%.*s", (int)(path + len - name), name));
+	len = sb_repo.len;
+	if (safe_create_leading_directories_const(sb_repo.buf))
+		die_errno(_("could not create leading directories of '%s'"),
+			  sb_repo.buf);
+	while (!stat(sb_repo.buf, &st)) {
+		counter++;
+		strbuf_setlen(&sb_repo, len);
+		strbuf_addf(&sb_repo, "%d", counter);
+	}
+	name = strrchr(sb_repo.buf, '/') + 1;
+	if (mkdir(sb_repo.buf, 0777))
+		die_errno(_("could not create directory of '%s'"), sb_repo.buf);
+
+	strbuf_addf(&sb_git, "%s/.git", path);
+	if (safe_create_leading_directories_const(sb_git.buf))
+		die_errno(_("could not create leading directories of '%s'"),
+			  sb_git.buf);
+
+	write_file(sb_git.buf, 1, "gitdir: %s/repos/%s\n",
+		   real_path(get_git_common_dir()), name);
+	/*
+	 * This is to keep resolve_ref() happy. We need a valid HEAD
+	 * or is_git_directory() will reject the directory. Any valid
+	 * value would do because this value will be ignored and
+	 * replaced at the next (real) checkout.
+	 */
+	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
+	write_file(sb.buf, 1, "%s\n", sha1_to_hex(new->commit->object.sha1));
+	strbuf_reset(&sb);
+	strbuf_addf(&sb, "%s/commondir", sb_repo.buf);
+	write_file(sb.buf, 1, "../..\n");
+
+	if (!opts->quiet)
+		fprintf_ln(stderr, _("Enter %s (identifier %s)"), path, name);
+
+	setenv("GIT_CHECKOUT_NEW_WORKTREE", "1", 1);
+	setenv(GIT_DIR_ENVIRONMENT, sb_git.buf, 1);
+	setenv(GIT_WORK_TREE_ENVIRONMENT, path, 1);
+	memset(&cp, 0, sizeof(cp));
+	cp.git_cmd = 1;
+	cp.argv = opts->saved_argv;
+	return run_command(&cp);
+}
+
 static int git_checkout_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "diff.ignoresubmodules")) {
@@ -1067,6 +1143,9 @@ static int checkout_branch(struct checkout_opts *opts,
 		die(_("Cannot switch branch to a non-commit '%s'"),
 		    new->name);
 
+	if (opts->new_worktree)
+		return prepare_linked_checkout(opts, new);
+
 	if (!new->commit && opts->new_branch) {
 		unsigned char rev[20];
 		int flag;
@@ -1109,6 +1188,8 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 			 N_("do not limit pathspecs to sparse entries only")),
 		OPT_HIDDEN_BOOL(0, "guess", &dwim_new_local_branch,
 				N_("second guess 'git checkout no-such-branch'")),
+		OPT_STRING(0, "to", &opts.new_worktree, N_("path"),
+			   N_("check a branch out in a separate working directory")),
 		OPT_END(),
 	};
 
@@ -1117,6 +1198,9 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	opts.overwrite_ignore = 1;
 	opts.prefix = prefix;
 
+	opts.saved_argv = xmalloc(sizeof(const char *) * (argc + 2));
+	memcpy(opts.saved_argv, argv, sizeof(const char *) * (argc + 1));
+
 	gitmodules_config();
 	git_config(git_checkout_config, &opts);
 
@@ -1125,6 +1209,11 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, options, checkout_usage,
 			     PARSE_OPT_KEEP_DASHDASH);
 
+	/* recursive execution from checkout_new_worktree() */
+	opts.new_worktree_mode = getenv("GIT_CHECKOUT_NEW_WORKTREE") != NULL;
+	if (opts.new_worktree_mode)
+		opts.new_worktree = NULL;
+
 	if (conflict_style) {
 		opts.merge = 1; /* implied */
 		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
diff --git a/path.c b/path.c
index 8a6586c..e41d6b3 100644
--- a/path.c
+++ b/path.c
@@ -92,7 +92,7 @@ static void replace_dir(struct strbuf *buf, int len, const char *newdir)
 
 static const char *common_list[] = {
 	"/branches", "/hooks", "/info", "/logs", "/lost-found", "/modules",
-	"/objects", "/refs", "/remotes", "/rr-cache", "/svn",
+	"/objects", "/refs", "/remotes", "/repos", "/rr-cache", "/svn",
 	"config", "gc.pid", "packed-refs", "shallow",
 	NULL
 };
diff --git a/t/t2025-checkout-to.sh b/t/t2025-checkout-to.sh
new file mode 100755
index 0000000..5ec49e2
--- /dev/null
+++ b/t/t2025-checkout-to.sh
@@ -0,0 +1,48 @@
+#!/bin/sh
+
+test_description='test git checkout --to'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit init
+'
+
+test_expect_success 'checkout --to not updating paths' '
+	test_must_fail git checkout --to -- init.t
+'
+
+test_expect_success 'checkout --to a new worktree' '
+	git checkout --to here master &&
+	(
+		cd here &&
+		test_cmp ../init.t init.t &&
+		git symbolic-ref HEAD >actual &&
+		echo refs/heads/master >expect &&
+		test_cmp expect actual &&
+		git fsck
+	)
+'
+
+test_expect_success 'checkout --to from a linked checkout' '
+	(
+		cd here &&
+		git checkout --to nested-here master
+		cd nested-here &&
+		git fsck
+	)
+'
+
+test_expect_success 'checkout --to a new worktree creating new branch' '
+	git checkout --to there -b newmaster master &&
+	(
+		cd there &&
+		test_cmp ../init.t init.t &&
+		git symbolic-ref HEAD >actual &&
+		echo refs/heads/newmaster >expect &&
+		test_cmp expect actual &&
+		git fsck
+	)
+'
+
+test_done
-- 
1.9.1.346.ga2b5940

[PATCH v7 23/31] checkout: clean up half-prepared directories in --to mode

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/checkout.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 81adb74..3167fd2 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -20,6 +20,7 @@
 #include "resolve-undo.h"
 #include "submodule.h"
 #include "argv-array.h"
+#include "sigchain.h"
 
 static const char * const checkout_usage[] = {
 	N_("git checkout [options] <branch>"),
@@ -814,6 +815,35 @@ static int switch_branches(const struct checkout_opts *opts,
 	return ret || writeout_error;
 }
 
+static const char *junk_work_tree;
+static const char *junk_git_dir;
+static int is_junk;
+static pid_t junk_pid;
+
+static void remove_junk(void)
+{
+	struct strbuf sb = STRBUF_INIT;
+	if (!is_junk || getpid() != junk_pid)
+		return;
+	if (junk_git_dir) {
+		strbuf_addstr(&sb, junk_git_dir);
+		remove_dir_recursively(&sb, 0);
+		strbuf_reset(&sb);
+	}
+	if (junk_work_tree) {
+		strbuf_addstr(&sb, junk_work_tree);
+		remove_dir_recursively(&sb, 0);
+	}
+	strbuf_release(&sb);
+}
+
+static void remove_junk_on_signal(int signo)
+{
+	remove_junk();
+	sigchain_pop(signo);
+	raise(signo);
+}
+
 static int prepare_linked_checkout(const struct checkout_opts *opts,
 				   struct branch_info *new)
 {
@@ -822,7 +852,7 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	const char *path = opts->new_worktree, *name;
 	struct stat st;
 	struct child_process cp;
-	int counter = 0, len;
+	int counter = 0, len, ret;
 
 	if (!new->commit)
 		die(_("no branch specified"));
@@ -848,13 +878,21 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 		strbuf_addf(&sb_repo, "%d", counter);
 	}
 	name = strrchr(sb_repo.buf, '/') + 1;
+
+	junk_pid = getpid();
+	atexit(remove_junk);
+	sigchain_push_common(remove_junk_on_signal);
+
 	if (mkdir(sb_repo.buf, 0777))
 		die_errno(_("could not create directory of '%s'"), sb_repo.buf);
+	junk_git_dir = sb_repo.buf;
+	is_junk = 1;
 
 	strbuf_addf(&sb_git, "%s/.git", path);
 	if (safe_create_leading_directories_const(sb_git.buf))
 		die_errno(_("could not create leading directories of '%s'"),
 			  sb_git.buf);
+	junk_work_tree = path;
 
 	write_file(sb_git.buf, 1, "gitdir: %s/repos/%s\n",
 		   real_path(get_git_common_dir()), name);
@@ -879,7 +917,14 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	memset(&cp, 0, sizeof(cp));
 	cp.git_cmd = 1;
 	cp.argv = opts->saved_argv;
-	return run_command(&cp);
+	ret = run_command(&cp);
+	if (!ret)
+		is_junk = 0;
+	strbuf_release(&sb);
+	strbuf_release(&sb_repo);
+	strbuf_release(&sb_git);
+	return ret;
+
 }
 
 static int git_checkout_config(const char *var, const char *value, void *cb)
-- 
1.9.1.346.ga2b5940

[PATCH v7 24/31] checkout: detach if the branch is already checked out elsewhere

[Nguyễn Thái Ngọc Duy]

The normal rule is anything outside refs/heads/ is detached. This
increases strictness of the rule a bit more: if the branch is checked
out (either in $GIT_COMMON_DIR/HEAD or any $GIT_DIR/repos/.../HEAD)
then it's detached as well.

A hint is given so the user knows where to go and do something there
if they still want to checkout undetached here.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/checkout.c     | 84 ++++++++++++++++++++++++++++++++++++++++++++++++++
 t/t2025-checkout-to.sh | 23 ++++++++++++--
 2 files changed, 104 insertions(+), 3 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 3167fd2..fe24766 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -432,6 +432,11 @@ struct branch_info {
 	const char *name; /* The short name used */
 	const char *path; /* The full name of a real branch */
 	struct commit *commit; /* The named commit */
+	/*
+	 * if not null the branch is detached because it's already
+	 * checked out in this checkout
+	 */
+	char *checkout;
 };
 
 static void setup_branch_path(struct branch_info *branch)
@@ -640,6 +645,11 @@ static void update_refs_for_switch(const struct checkout_opts *opts,
 			if (old->path && advice_detached_head)
 				detach_advice(new->name);
 			describe_detached_head(_("HEAD is now at"), new->commit);
+			if (new->checkout && !*new->checkout)
+				fprintf(stderr, _("hint: the main checkout is holding this branch\n"));
+			else if (new->checkout)
+				fprintf(stderr, _("hint: the linked checkout %s is holding this branch\n"),
+					new->checkout);
 		}
 	} else if (new->path) {	/* Switch branches. */
 		create_symref("HEAD", new->path, msg.buf);
@@ -982,6 +992,71 @@ static const char *unique_tracking_name(const char *name, unsigned char *sha1)
 	return NULL;
 }
 
+static int check_linked_checkout(struct branch_info *new,
+				  const char *name, const char *path)
+{
+	struct strbuf sb = STRBUF_INIT;
+	const char *start, *end;
+	if (strbuf_read_file(&sb, path, 0) < 0 ||
+	    !skip_prefix(sb.buf, "ref:", &start)) {
+		strbuf_release(&sb);
+		return 0;
+	}
+
+	while (isspace(*start))
+		start++;
+	end = start;
+	while (*end && !isspace(*end))
+		end++;
+	if (!strncmp(start, new->path, end - start) &&
+	    new->path[end - start] == '\0') {
+		strbuf_release(&sb);
+		new->path = NULL; /* detach */
+		new->checkout = xstrdup(name); /* reason */
+		return 1;
+	}
+	strbuf_release(&sb);
+	return 0;
+}
+
+static void check_linked_checkouts(struct branch_info *new)
+{
+	struct strbuf path = STRBUF_INIT;
+	DIR *dir;
+	struct dirent *d;
+
+	strbuf_addf(&path, "%s/repos", get_git_common_dir());
+	if ((dir = opendir(path.buf)) == NULL) {
+		strbuf_release(&path);
+		return;
+	}
+
+	strbuf_reset(&path);
+	strbuf_addf(&path, "%s/HEAD", get_git_common_dir());
+	/*
+	 * $GIT_COMMON_DIR/HEAD is practically outside
+	 * $GIT_DIR so resolve_ref_unsafe() won't work (it
+	 * uses git_path). Parse the ref ourselves.
+	 */
+	if (check_linked_checkout(new, "", path.buf)) {
+		strbuf_release(&path);
+		closedir(dir);
+		return;
+	}
+
+	while ((d = readdir(dir)) != NULL) {
+		if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
+			continue;
+		strbuf_reset(&path);
+		strbuf_addf(&path, "%s/repos/%s/HEAD",
+			    get_git_common_dir(), d->d_name);
+		if (check_linked_checkout(new, d->d_name, path.buf))
+			break;
+	}
+	strbuf_release(&path);
+	closedir(dir);
+}
+
 static int parse_branchname_arg(int argc, const char **argv,
 				int dwim_new_local_branch_ok,
 				struct branch_info *new,
@@ -1109,6 +1184,15 @@ static int parse_branchname_arg(int argc, const char **argv,
 	else
 		new->path = NULL; /* not an existing branch */
 
+	if (new->path) {
+		unsigned char sha1[20];
+		int flag;
+		char *head_ref = resolve_refdup("HEAD", sha1, 0, &flag);
+		if (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path))
+			check_linked_checkouts(new);
+		free(head_ref);
+	}
+
 	new->commit = lookup_commit_reference_gently(rev, 1);
 	if (!new->commit) {
 		/* not a commit */
diff --git a/t/t2025-checkout-to.sh b/t/t2025-checkout-to.sh
index 5ec49e2..20e3dc7 100755
--- a/t/t2025-checkout-to.sh
+++ b/t/t2025-checkout-to.sh
@@ -13,13 +13,14 @@ test_expect_success 'checkout --to not updating paths' '
 '
 
 test_expect_success 'checkout --to a new worktree' '
+	git rev-parse HEAD >expect &&
 	git checkout --to here master &&
 	(
 		cd here &&
 		test_cmp ../init.t init.t &&
-		git symbolic-ref HEAD >actual &&
-		echo refs/heads/master >expect &&
-		test_cmp expect actual &&
+		test_must_fail git symbolic-ref HEAD &&
+		git rev-parse HEAD >actual &&
+		test_cmp ../expect actual &&
 		git fsck
 	)
 '
@@ -45,4 +46,20 @@ test_expect_success 'checkout --to a new worktree creating new branch' '
 	)
 '
 
+test_expect_success 'detach if the same branch is already checked out' '
+	(
+		cd here &&
+		git checkout newmaster &&
+		test_must_fail git symbolic-ref HEAD
+	)
+'
+
+test_expect_success 'not detach on re-checking out current branch' '
+	(
+		cd there &&
+		git checkout newmaster &&
+		git symbolic-ref HEAD
+	)
+'
+
 test_done
-- 
1.9.1.346.ga2b5940

[PATCH v7 25/31] prune: strategies for linked checkouts

[Nguyễn Thái Ngọc Duy]

(alias R=$GIT_COMMON_DIR/repos/<id>)

 - linked checkouts are supposed to keep its location in $R/gitdir up
   to date. The use case is auto fixup after a manual checkout move.

 - linked checkouts are supposed to update mtime of $R/gitdir. If
   $R/gitdir's mtime is older than a limit, and it points to nowhere,
   repos/<id> is to be pruned.

 - If $R/locked exists, repos/<id> is not supposed to be pruned. If
   $R/locked exists and $R/gitdir's mtime is older than a really long
   limit, warn about old unused repo.

 - "git checkout --to" is supposed to make a hard link named $R/link
   pointing to the .git file on supported file systems to help detect
   the user manually deleting the checkout. If $R/link exists and its
   link count is greated than 1, the repo is kept.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git-prune.txt                |  3 +
 Documentation/gitrepository-layout.txt     | 19 ++++++
 builtin/checkout.c                         | 14 +++++
 builtin/prune.c                            | 99 ++++++++++++++++++++++++++++++
 setup.c                                    | 13 ++++
 t/t2026-prune-linked-checkouts.sh (new +x) | 84 +++++++++++++++++++++++++
 6 files changed, 232 insertions(+)
 create mode 100755 t/t2026-prune-linked-checkouts.sh

diff --git a/Documentation/git-prune.txt b/Documentation/git-prune.txt
index 7a493c8..50e39ec 100644
--- a/Documentation/git-prune.txt
+++ b/Documentation/git-prune.txt
@@ -48,6 +48,9 @@ OPTIONS
 --expire <time>::
 	Only expire loose objects older than <time>.
 
+--repos::
+	Prune directories in $GIT_DIR/repos.
+
 <head>...::
 	In addition to objects
 	reachable from any of our references, keep objects
diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
index 543d874..bed4f1a 100644
--- a/Documentation/gitrepository-layout.txt
+++ b/Documentation/gitrepository-layout.txt
@@ -256,6 +256,25 @@ repos::
 	$GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/repos" will be
 	used instead.
 
+repos/<id>/gitdir::
+	A text file containing the absolute path back to the .git file
+	that points to here. This is used to check if the linked
+	repository has been manually removed and there is no need to
+	keep this directory any more. mtime of this file should be
+	updated every time the linked repository is accessed.
+
+repos/<id>/locked::
+	If this file exists, the linked repository may be on a
+	portable device and not available. It does not mean that the
+	linked repository is gone and `repos/<id>` could be
+	removed. The file's content contains a reason string on why
+	the repository is locked.
+
+repos/<id>/link::
+	If this file exists, it is a hard link to the linked .git
+	file. It is used to detect if the linked repository is
+	manually removed.
+
 SEE ALSO
 --------
 linkgit:git-init[1],
diff --git a/builtin/checkout.c b/builtin/checkout.c
index fe24766..5b93f49 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -898,12 +898,22 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	junk_git_dir = sb_repo.buf;
 	is_junk = 1;
 
+	/*
+	 * lock the incomplete repo so prune won't delete it, unlock
+	 * after the preparation is over.
+	 */
+	strbuf_addf(&sb, "%s/locked", sb_repo.buf);
+	write_file(sb.buf, 1, "initializing\n");
+
 	strbuf_addf(&sb_git, "%s/.git", path);
 	if (safe_create_leading_directories_const(sb_git.buf))
 		die_errno(_("could not create leading directories of '%s'"),
 			  sb_git.buf);
 	junk_work_tree = path;
 
+	strbuf_reset(&sb);
+	strbuf_addf(&sb, "%s/gitdir", sb_repo.buf);
+	write_file(sb.buf, 1, "%s\n", real_path(sb_git.buf));
 	write_file(sb_git.buf, 1, "gitdir: %s/repos/%s\n",
 		   real_path(get_git_common_dir()), name);
 	/*
@@ -912,6 +922,7 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	 * value would do because this value will be ignored and
 	 * replaced at the next (real) checkout.
 	 */
+	strbuf_reset(&sb);
 	strbuf_addf(&sb, "%s/HEAD", sb_repo.buf);
 	write_file(sb.buf, 1, "%s\n", sha1_to_hex(new->commit->object.sha1));
 	strbuf_reset(&sb);
@@ -930,6 +941,9 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
 	ret = run_command(&cp);
 	if (!ret)
 		is_junk = 0;
+	strbuf_reset(&sb);
+	strbuf_addf(&sb, "%s/locked", sb_repo.buf);
+	unlink_or_warn(sb.buf);
 	strbuf_release(&sb);
 	strbuf_release(&sb_repo);
 	strbuf_release(&sb_git);
diff --git a/builtin/prune.c b/builtin/prune.c
index 144a3bd..28b7adf 100644
--- a/builtin/prune.c
+++ b/builtin/prune.c
@@ -112,6 +112,95 @@ static void prune_object_dir(const char *path)
 	}
 }
 
+static int prune_repo_dir(const char *id, struct stat *st, struct strbuf *reason)
+{
+	char *path;
+	int fd, len;
+
+	if (!is_directory(git_path("repos/%s", id))) {
+		strbuf_addf(reason, _("Removing repos/%s: not a valid directory"), id);
+		return 1;
+	}
+	if (file_exists(git_path("repos/%s/locked", id)))
+		return 0;
+	if (stat(git_path("repos/%s/gitdir", id), st)) {
+		st->st_mtime = expire;
+		strbuf_addf(reason, _("Removing repos/%s: gitdir file does not exist"), id);
+		return 1;
+	}
+	fd = open(git_path("repos/%s/gitdir", id), O_RDONLY);
+	if (fd < 0) {
+		st->st_mtime = expire;
+		strbuf_addf(reason, _("Removing repos/%s: unable to read gitdir file (%s)"),
+			    id, strerror(errno));
+		return 1;
+	}
+	len = st->st_size;
+	path = xmalloc(len + 1);
+	read_in_full(fd, path, len);
+	close(fd);
+	while (len && (path[len - 1] == '\n' || path[len - 1] == '\r'))
+		len--;
+	if (!len) {
+		st->st_mtime = expire;
+		strbuf_addf(reason, _("Removing repos/%s: invalid gitdir file"), id);
+		free(path);
+		return 1;
+	}
+	path[len] = '\0';
+	if (!file_exists(path)) {
+		struct stat st_link;
+		free(path);
+		/*
+		 * the repo is moved manually and has not been
+		 * accessed since?
+		 */
+		if (!stat(git_path("repos/%s/link", id), &st_link) &&
+		    st_link.st_nlink > 1)
+			return 0;
+		strbuf_addf(reason, _("Removing repos/%s: gitdir file points to non-existent location"), id);
+		return 1;
+	}
+	free(path);
+	return 0;
+}
+
+static void prune_repos_dir(void)
+{
+	struct strbuf reason = STRBUF_INIT;
+	struct strbuf path = STRBUF_INIT;
+	DIR *dir = opendir(git_path("repos"));
+	struct dirent *d;
+	int ret;
+	struct stat st;
+	if (!dir)
+		return;
+	while ((d = readdir(dir)) != NULL) {
+		if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
+			continue;
+		strbuf_reset(&reason);
+		if (!prune_repo_dir(d->d_name, &st, &reason) ||
+		    st.st_mtime > expire)
+			continue;
+		if (show_only || verbose)
+			printf("%s\n", reason.buf);
+		if (show_only)
+			continue;
+		strbuf_reset(&path);
+		strbuf_addstr(&path, git_path("repos/%s", d->d_name));
+		ret = remove_dir_recursively(&path, 0);
+		if (ret < 0 && errno == ENOTDIR)
+			ret = unlink(path.buf);
+		if (ret)
+			error(_("failed to remove: %s"), strerror(errno));
+	}
+	closedir(dir);
+	if (!show_only)
+		rmdir(git_path("repos"));
+	strbuf_release(&reason);
+	strbuf_release(&path);
+}
+
 /*
  * Write errors (particularly out of space) can result in
  * failed temporary packs (and more rarely indexes and other
@@ -138,10 +227,12 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
 {
 	struct rev_info revs;
 	struct progress *progress = NULL;
+	int prune_repos = 0;
 	const struct option options[] = {
 		OPT__DRY_RUN(&show_only, N_("do not remove, show only")),
 		OPT__VERBOSE(&verbose, N_("report pruned objects")),
 		OPT_BOOL(0, "progress", &show_progress, N_("show progress")),
+		OPT_BOOL(0, "repos", &prune_repos, N_("prune .git/repos/")),
 		OPT_EXPIRY_DATE(0, "expire", &expire,
 				N_("expire objects older than <time>")),
 		OPT_END()
@@ -154,6 +245,14 @@ int cmd_prune(int argc, const char **argv, const char *prefix)
 	init_revisions(&revs, prefix);
 
 	argc = parse_options(argc, argv, prefix, options, prune_usage, 0);
+
+	if (prune_repos) {
+		if (argc)
+			die(_("--repos does not take extra arguments"));
+		prune_repos_dir();
+		return 0;
+	}
+
 	while (argc--) {
 		unsigned char sha1[20];
 		const char *name = *argv++;
diff --git a/setup.c b/setup.c
index 8f90bc3..da2d669 100644
--- a/setup.c
+++ b/setup.c
@@ -390,6 +390,17 @@ static int check_repository_format_gently(const char *gitdir, int *nongit_ok)
 	return ret;
 }
 
+static void update_linked_gitdir(const char *gitfile, const char *gitdir)
+{
+	struct strbuf path = STRBUF_INIT;
+	struct stat st;
+
+	strbuf_addf(&path, "%s/gitfile", gitdir);
+	if (stat(path.buf, &st) || st.st_mtime + 24 * 3600 < time(NULL))
+		write_file(path.buf, 0, "%s\n", gitfile);
+	strbuf_release(&path);
+}
+
 /*
  * Try to read the location of the git directory from the .git file,
  * return path to git directory if found.
@@ -438,6 +449,8 @@ const char *read_gitfile(const char *path)
 
 	if (!is_git_directory(dir))
 		die("Not a git repository: %s", dir);
+
+	update_linked_gitdir(path, dir);
 	path = real_path(dir);
 
 	free(buf);
diff --git a/t/t2026-prune-linked-checkouts.sh b/t/t2026-prune-linked-checkouts.sh
new file mode 100755
index 0000000..4ccfa4e
--- /dev/null
+++ b/t/t2026-prune-linked-checkouts.sh
@@ -0,0 +1,84 @@
+#!/bin/sh
+
+test_description='prune $GIT_DIR/repos'
+
+. ./test-lib.sh
+
+test_expect_success 'prune --repos on normal repo' '
+	git prune --repos &&
+	test_must_fail git prune --repos abc
+'
+
+test_expect_success 'prune files inside $GIT_DIR/repos' '
+	mkdir .git/repos &&
+	: >.git/repos/abc &&
+	git prune --repos --verbose >actual &&
+	cat >expect <<EOF &&
+Removing repos/abc: not a valid directory
+EOF
+	test_i18ncmp expect actual &&
+	! test -f .git/repos/abc &&
+	! test -d .git/repos
+'
+
+test_expect_success 'prune directories without gitdir' '
+	mkdir -p .git/repos/def/abc &&
+	: >.git/repos/def/def &&
+	cat >expect <<EOF &&
+Removing repos/def: gitdir file does not exist
+EOF
+	git prune --repos --verbose >actual &&
+	test_i18ncmp expect actual &&
+	! test -d .git/repos/def &&
+	! test -d .git/repos
+'
+
+test_expect_success POSIXPERM 'prune directories with unreadable gitdir' '
+	mkdir -p .git/repos/def/abc &&
+	: >.git/repos/def/def &&
+	: >.git/repos/def/gitdir &&
+	chmod u-r .git/repos/def/gitdir &&
+	git prune --repos --verbose >actual &&
+	test_i18ngrep "Removing repos/def: unable to read gitdir file" actual &&
+	! test -d .git/repos/def &&
+	! test -d .git/repos
+'
+
+test_expect_success 'prune directories with invalid gitdir' '
+	mkdir -p .git/repos/def/abc &&
+	: >.git/repos/def/def &&
+	: >.git/repos/def/gitdir &&
+	git prune --repos --verbose >actual &&
+	test_i18ngrep "Removing repos/def: invalid gitdir file" actual &&
+	! test -d .git/repos/def &&
+	! test -d .git/repos
+'
+
+test_expect_success 'prune directories with gitdir pointing to nowhere' '
+	mkdir -p .git/repos/def/abc &&
+	: >.git/repos/def/def &&
+	echo "$TRASH_DIRECTORY"/nowhere >.git/repos/def/gitdir &&
+	git prune --repos --verbose >actual &&
+	test_i18ngrep "Removing repos/def: gitdir file points to non-existent location" actual &&
+	! test -d .git/repos/def &&
+	! test -d .git/repos
+'
+
+test_expect_success 'not prune locked checkout' '
+	test_when_finished rm -r .git/repos
+	mkdir -p .git/repos/ghi &&
+	: >.git/repos/ghi/locked &&
+	git prune --repos &&
+	test -d .git/repos/ghi
+'
+
+test_expect_success 'not prune recent checkouts' '
+	test_when_finished rm -r .git/repos
+	mkdir zz &&
+	mkdir -p .git/repos/jlm &&
+	echo "$TRASH_DIRECTORY"/zz >.git/repos/jlm/gitdir &&
+	git prune --repos --verbose &&
+	test -d .git/repos/jlm
+'
+
+test_done
-- 
1.9.1.346.ga2b5940

[PATCH v7 26/31] gc: style change -- no SP before closing bracket

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/gc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index 8d219d8..3bfb990 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -298,7 +298,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 	argv_array_pushl(&pack_refs_cmd, "pack-refs", "--all", "--prune", NULL);
 	argv_array_pushl(&reflog, "reflog", "expire", "--all", NULL);
 	argv_array_pushl(&repack, "repack", "-d", "-l", NULL);
-	argv_array_pushl(&prune, "prune", "--expire", NULL );
+	argv_array_pushl(&prune, "prune", "--expire", NULL);
 	argv_array_pushl(&rerere, "rerere", "gc", NULL);
 
 	git_config(gc_config, NULL);
-- 
1.9.1.346.ga2b5940

[PATCH v7 27/31] gc: factor out gc.pruneexpire parsing code

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/gc.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/builtin/gc.c b/builtin/gc.c
index 3bfb990..e38c902 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -55,6 +55,17 @@ static void remove_pidfile_on_signal(int signo)
 	raise(signo);
 }
 
+static int git_config_date_string(const char **output,
+				  const char *var, const char *value)
+{
+	if (value && strcmp(value, "now")) {
+		unsigned long now = approxidate("now");
+		if (approxidate(value) >= now)
+			return error(_("Invalid %s: '%s'"), var, value);
+	}
+	return git_config_string(output, var, value);
+}
+
 static int gc_config(const char *var, const char *value, void *cb)
 {
 	if (!strcmp(var, "gc.packrefs")) {
@@ -84,14 +95,8 @@ static int gc_config(const char *var, const char *value, void *cb)
 		detach_auto = git_config_bool(var, value);
 		return 0;
 	}
-	if (!strcmp(var, "gc.pruneexpire")) {
-		if (value && strcmp(value, "now")) {
-			unsigned long now = approxidate("now");
-			if (approxidate(value) >= now)
-				return error(_("Invalid %s: '%s'"), var, value);
-		}
-		return git_config_string(&prune_expire, var, value);
-	}
+	if (!strcmp(var, "gc.pruneexpire"))
+		return git_config_date_string(&prune_expire, var, value);
 	return git_default_config(var, value, cb);
 }
 
-- 
1.9.1.346.ga2b5940

[PATCH v7 28/31] gc: support prune --repos

[Nguyễn Thái Ngọc Duy]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/config.txt |  7 +++++++
 builtin/gc.c             | 11 +++++++++++
 2 files changed, 18 insertions(+)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 286e539..57999fa 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1211,6 +1211,13 @@ gc.pruneexpire::
 	"now" may be used to disable this  grace period and always prune
 	unreachable objects immediately.
 
+gc.prunereposexpire::
+	When 'git gc' is run, it will call
+	'prune --repos --expire 3.months.ago'.
+	Override the grace period with this config variable. The value
+	"now" may be used to disable the grace period and prune
+	$GIT_DIR/repos immediately.
+
 gc.reflogexpire::
 gc.<pattern>.reflogexpire::
 	'git reflog expire' removes reflog entries older than
diff --git a/builtin/gc.c b/builtin/gc.c
index e38c902..0c65808 100644
--- a/builtin/gc.c
+++ b/builtin/gc.c
@@ -33,11 +33,13 @@ static int gc_auto_threshold = 6700;
 static int gc_auto_pack_limit = 50;
 static int detach_auto = 1;
 static const char *prune_expire = "2.weeks.ago";
+static const char *prune_repos_expire = "3.months.ago";
 
 static struct argv_array pack_refs_cmd = ARGV_ARRAY_INIT;
 static struct argv_array reflog = ARGV_ARRAY_INIT;
 static struct argv_array repack = ARGV_ARRAY_INIT;
 static struct argv_array prune = ARGV_ARRAY_INIT;
+static struct argv_array prune_repos = ARGV_ARRAY_INIT;
 static struct argv_array rerere = ARGV_ARRAY_INIT;
 
 static char *pidfile;
@@ -97,6 +99,8 @@ static int gc_config(const char *var, const char *value, void *cb)
 	}
 	if (!strcmp(var, "gc.pruneexpire"))
 		return git_config_date_string(&prune_expire, var, value);
+	if (!strcmp(var, "gc.prunereposexpire"))
+		return git_config_date_string(&prune_repos_expire, var, value);
 	return git_default_config(var, value, cb);
 }
 
@@ -304,6 +308,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 	argv_array_pushl(&reflog, "reflog", "expire", "--all", NULL);
 	argv_array_pushl(&repack, "repack", "-d", "-l", NULL);
 	argv_array_pushl(&prune, "prune", "--expire", NULL);
+	argv_array_pushl(&prune_repos, "prune", "--repos", "--expire", NULL);
 	argv_array_pushl(&rerere, "rerere", "gc", NULL);
 
 	git_config(gc_config, NULL);
@@ -373,6 +378,12 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 			return error(FAILED_RUN, prune.argv[0]);
 	}
 
+	if (prune_repos_expire) {
+		argv_array_push(&prune_repos, prune_repos_expire);
+		if (run_command_v_opt(prune_repos.argv, RUN_GIT_CMD))
+			return error(FAILED_RUN, prune_repos.argv[0]);
+	}
+
 	if (run_command_v_opt(rerere.argv, RUN_GIT_CMD))
 		return error(FAILED_RUN, rerere.argv[0]);
 
-- 
1.9.1.346.ga2b5940

[PATCH v7 29/31] count-objects: report unused files in $GIT_DIR/repos/...

[Nguyễn Thái Ngọc Duy]

In linked checkouts, borrowed parts like config is taken from
$GIT_COMMON_DIR. $GIT_DIR/config is never used. Report them as
garbage.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/count-objects.c |  4 +++-
 cache.h                 |  1 +
 path.c                  | 29 +++++++++++++++++++++++++++--
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/builtin/count-objects.c b/builtin/count-objects.c
index a7f70cb..d3a1620 100644
--- a/builtin/count-objects.c
+++ b/builtin/count-objects.c
@@ -102,8 +102,10 @@ int cmd_count_objects(int argc, const char **argv, const char *prefix)
 	/* we do not take arguments other than flags for now */
 	if (argc)
 		usage_with_options(count_objects_usage, opts);
-	if (verbose)
+	if (verbose) {
 		report_garbage = real_report_garbage;
+		report_linked_checkout_garbage();
+	}
 	memcpy(path, objdir, len);
 	if (len && objdir[len-1] != '/')
 		path[len++] = '/';
diff --git a/cache.h b/cache.h
index bf4d15e..12f0fc0 100644
--- a/cache.h
+++ b/cache.h
@@ -690,6 +690,7 @@ extern const char *mkpath(const char *fmt, ...) __attribute__((format (printf, 1
 extern const char *git_path(const char *fmt, ...) __attribute__((format (printf, 1, 2)));
 extern const char *git_path_submodule(const char *path, const char *fmt, ...)
 	__attribute__((format (printf, 2, 3)));
+extern void report_linked_checkout_garbage(void);
 
 /*
  * Return the name of the file in the local object database that would
diff --git a/path.c b/path.c
index e41d6b3..b5af137 100644
--- a/path.c
+++ b/path.c
@@ -4,6 +4,7 @@
 #include "cache.h"
 #include "strbuf.h"
 #include "string-list.h"
+#include "dir.h"
 
 static int get_st_mode_bits(const char *path, int *mode)
 {
@@ -91,9 +92,9 @@ static void replace_dir(struct strbuf *buf, int len, const char *newdir)
 }
 
 static const char *common_list[] = {
-	"/branches", "/hooks", "/info", "/logs", "/lost-found", "/modules",
+	"/branches", "/hooks", "/info", "!/logs", "/lost-found", "/modules",
 	"/objects", "/refs", "/remotes", "/repos", "/rr-cache", "/svn",
-	"config", "gc.pid", "packed-refs", "shallow",
+	"config", "!gc.pid", "packed-refs", "shallow",
 	NULL
 };
 
@@ -107,6 +108,8 @@ static void update_common_dir(struct strbuf *buf, int git_dir_len)
 	for (p = common_list; *p; p++) {
 		const char *path = *p;
 		int is_dir = 0;
+		if (*path == '!')
+			path++;
 		if (*path == '/') {
 			path++;
 			is_dir = 1;
@@ -122,6 +125,28 @@ static void update_common_dir(struct strbuf *buf, int git_dir_len)
 	}
 }
 
+void report_linked_checkout_garbage(void)
+{
+	struct strbuf sb = STRBUF_INIT;
+	const char **p;
+	int len;
+
+	if (!git_common_dir_env)
+		return;
+	strbuf_addf(&sb, "%s/", get_git_dir());
+	len = sb.len;
+	for (p = common_list; *p; p++) {
+		const char *path = *p;
+		if (*path == '!')
+			continue;
+		strbuf_setlen(&sb, len);
+		strbuf_addstr(&sb, path);
+		if (file_exists(sb.buf))
+			report_garbage("unused in linked checkout", sb.buf);
+	}
+	strbuf_release(&sb);
+}
+
 static void adjust_git_path(struct strbuf *buf, int git_dir_len)
 {
 	const char *base = buf->buf + git_dir_len;
-- 
1.9.1.346.ga2b5940

[PATCH v7 30/31] git_path(): keep "info/sparse-checkout" per work-tree

[Nguyễn Thái Ngọc Duy]

Currently git_path("info/sparse-checkout") resolves to
$GIT_COMMON_DIR/info/sparse-checkout in multiple worktree mode. It
makes more sense for the sparse checkout patterns to be per worktree,
so you can have multiple checkouts with different parts of the tree.

With this, "git checkout --to <new>" on a sparse checkout will create
<new> as a full checkout. Which is expected, it's how a new checkout
is made. The user can reshape the worktree afterwards.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 path.c                | 3 ++-
 t/t0060-path-utils.sh | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/path.c b/path.c
index b5af137..b1dd2bc 100644
--- a/path.c
+++ b/path.c
@@ -103,7 +103,8 @@ static void update_common_dir(struct strbuf *buf, int git_dir_len)
 	char *base = buf->buf + git_dir_len;
 	const char **p;
 
-	if (is_dir_file(base, "logs", "HEAD"))
+	if (is_dir_file(base, "logs", "HEAD") ||
+	    is_dir_file(base, "info", "sparse-checkout"))
 		return;	/* keep this in $GIT_DIR */
 	for (p = common_list; *p; p++) {
 		const char *path = *p;
diff --git a/t/t0060-path-utils.sh b/t/t0060-path-utils.sh
index 2dabcef..da82aab 100755
--- a/t/t0060-path-utils.sh
+++ b/t/t0060-path-utils.sh
@@ -269,6 +269,7 @@ test_git_path GIT_COMMON_DIR=bar logs/HEAD                .git/logs/HEAD
 test_git_path GIT_COMMON_DIR=bar objects                  bar/objects
 test_git_path GIT_COMMON_DIR=bar objects/bar              bar/objects/bar
 test_git_path GIT_COMMON_DIR=bar info/exclude             bar/info/exclude
+test_git_path GIT_COMMON_DIR=bar info/sparse-checkout     .git/info/sparse-checkout
 test_git_path GIT_COMMON_DIR=bar remotes/bar              bar/remotes/bar
 test_git_path GIT_COMMON_DIR=bar branches/bar             bar/branches/bar
 test_git_path GIT_COMMON_DIR=bar logs/refs/heads/master   bar/logs/refs/heads/master
-- 
1.9.1.346.ga2b5940

[PATCH v7 31/31] checkout: don't require a work tree when checking out into a new one

[Nguyễn Thái Ngọc Duy]

From: Dennis Kaarsemaker <dennis@kaarsemaker.net>

For normal use cases, it does not make sense for 'checkout' to work on
a bare repository, without a worktree. But "checkout --to" is an
exception because it _creates_ a new worktree. Allow this option to
run on bare repositories.

People who check out from a bare repository should remember that
core.logallrefupdates is off by default and it should be turned back
on. `--to` cannot do this automatically behind the user's back because
some user may deliberately want no reflog.

For people interested in repository setup/discovery code,
is_bare_repository_cfg (aka "core.bare") is unchanged by this patch,
which means 'true' by default for bare repos. Fortunately when we get
the repo through a linked checkout, is_bare_repository_cfg is never
used. So all is still good.

[nd: commit message]

Signed-off-by: Dennis Kaarsemaker <dennis@kaarsemaker.net>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 builtin/checkout.c     |  3 +++
 git.c                  |  2 +-
 t/t2025-checkout-to.sh | 15 +++++++++++++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index 5b93f49..c83f476 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -1357,6 +1357,9 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 	if (opts.new_worktree_mode)
 		opts.new_worktree = NULL;
 
+	if (!opts.new_worktree)
+		setup_work_tree();
+
 	if (conflict_style) {
 		opts.merge = 1; /* implied */
 		git_xmerge_config("merge.conflictstyle", conflict_style, NULL);
diff --git a/git.c b/git.c
index 5b6c761..7426651 100644
--- a/git.c
+++ b/git.c
@@ -383,7 +383,7 @@ static struct cmd_struct commands[] = {
 	{ "check-ignore", cmd_check_ignore, RUN_SETUP | NEED_WORK_TREE },
 	{ "check-mailmap", cmd_check_mailmap, RUN_SETUP },
 	{ "check-ref-format", cmd_check_ref_format },
-	{ "checkout", cmd_checkout, RUN_SETUP | NEED_WORK_TREE },
+	{ "checkout", cmd_checkout, RUN_SETUP },
 	{ "checkout-index", cmd_checkout_index,
 		RUN_SETUP | NEED_WORK_TREE},
 	{ "cherry", cmd_cherry, RUN_SETUP },
diff --git a/t/t2025-checkout-to.sh b/t/t2025-checkout-to.sh
index 20e3dc7..b0d97a0 100755
--- a/t/t2025-checkout-to.sh
+++ b/t/t2025-checkout-to.sh
@@ -62,4 +62,19 @@ test_expect_success 'not detach on re-checking out current branch' '
 	)
 '
 
+test_expect_success 'checkout --to from a bare repo' '
+	(
+		git clone --bare . bare &&
+		cd bare &&
+		git checkout --to ../there2 master
+	)
+'
+
+test_expect_success 'checkout from a bare repo without --to' '
+	(
+		cd bare &&
+		test_must_fail git checkout master
+	)
+'
+
 test_done
-- 
1.9.1.346.ga2b5940

Re: [PATCH v6 28/32] gc: style change -- no SP before closing bracket

[Junio C Hamano]

On Wed, Jul 9, 2014 at 2:47 AM, Eric Sunshine <sunshine@sunshineco.com> wrote:
> On Wed, Jul 9, 2014 at 3:33 AM, Nguyễn Thái Ngọc Duy <pclouds@gmail.com> wrote:
>
> Yet, there is a space after the opening '{'. So, this is now
> inconsistently formatted as:
>
>     { foo, bar}
>

So, if we drop the other hunk and keep only the one below,
the patch needs to be retitled with s/bracket/parenthesis/...

>> @@ -298,7 +298,7 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
>>         argv_array_pushl(&pack_refs_cmd, "pack-refs", "--all", "--prune", NULL);
>>         argv_array_pushl(&reflog, "reflog", "expire", "--all", NULL);
>>         argv_array_pushl(&repack, "repack", "-d", "-l", NULL);
>> -       argv_array_pushl(&prune, "prune", "--expire", NULL );
>> +       argv_array_pushl(&prune, "prune", "--expire", NULL);
>>         argv_array_pushl(&rerere, "rerere", "gc", NULL);
>>
>>         git_config(gc_config, NULL);
>> --
>> 1.9.1.346.ga2b5940

Re: [PATCH v7 00/31] Support multiple checkouts

[Junio C Hamano]

Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:

>  	fd = open(git_path("repos/%s/gitdir", id), O_RDONLY);
> ...
> -	while (path[len - 1] == '\n' || path[len - 1] == '\r')
> +	while (len && (path[len - 1] == '\n' || path[len - 1] == '\r'))
>  		len--;

Do we anticipate (or even allow/endorse) that end users will edit
this file with a random editor?  And, to a lessor degree, the same
question on the reading side.  Do we encourage users to directly
read from this file to learn something about their repository?

If we are the only tool that writes into this file, and if we are
the only tool to be used to read (and use) the contents of this
file, I do not see the need to cater to LF vs CRLF line endings.

Re: [PATCH v7 00/31] Support multiple checkouts

[Duy Nguyen]

On Mon, Jul 14, 2014 at 11:45 AM, Junio C Hamano <gitster@pobox.com> wrote:
> Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:
>
>>       fd = open(git_path("repos/%s/gitdir", id), O_RDONLY);
>> ...
>> -     while (path[len - 1] == '\n' || path[len - 1] == '\r')
>> +     while (len && (path[len - 1] == '\n' || path[len - 1] == '\r'))
>>               len--;
>
> Do we anticipate (or even allow/endorse) that end users will edit
> this file with a random editor?  And, to a lessor degree, the same
> question on the reading side.  Do we encourage users to directly
> read from this file to learn something about their repository?
>
> If we are the only tool that writes into this file, and if we are
> the only tool to be used to read (and use) the contents of this
> file, I do not see the need to cater to LF vs CRLF line endings.

No I don't expect users to go and change these files by themselves.
But once directory structure is documented, other tools might appear
and scripts on Windows may just append CRLF by default.
-- 
Duy

Re: [PATCH v7 00/31] Support multiple checkouts

[Junio C Hamano]

Duy Nguyen <pclouds@gmail.com> writes:

> On Mon, Jul 14, 2014 at 11:45 AM, Junio C Hamano <gitster@pobox.com> wrote:
>> Nguyễn Thái Ngọc Duy  <pclouds@gmail.com> writes:
>>
>>>       fd = open(git_path("repos/%s/gitdir", id), O_RDONLY);
>>> ...
>>> -     while (path[len - 1] == '\n' || path[len - 1] == '\r')
>>> +     while (len && (path[len - 1] == '\n' || path[len - 1] == '\r'))
>>>               len--;
>>
>> Do we anticipate (or even allow/endorse) that end users will edit
>> this file with a random editor?  And, to a lessor degree, the same
>> question on the reading side.  Do we encourage users to directly
>> read from this file to learn something about their repository?
>>
>> If we are the only tool that writes into this file, and if we are
>> the only tool to be used to read (and use) the contents of this
>> file, I do not see the need to cater to LF vs CRLF line endings.
>
> No I don't expect users to go and change these files by themselves.
> But once directory structure is documented, other tools might appear
> and scripts on Windows may just append CRLF by default.

Essentially you are encouraging them to edit this file with a random
editor, bypassing Git, then.

Re: [PATCH v7 22/31] checkout: support checking out into a new working directory

[Max Kirillov]

Hi.

On Sun, Jul 13, 2014 at 11:50:59AM +0700, Nguyễn Thái Ngọc Duy wrote:
> +MULTIPLE CHECKOUT MODE
> +-------------------------------

This generates incorrect html for me, making all section
until next heading "EXAMPLES" into a preformatted text. If I
justify the line of dashes to be the exactly same width as
header it starts generating correctly looking html.

I'm not sure which software to refer to. I mostly use Debian
stable. The installed version of asciidocs is 8.6.7-1. I
suppose the line really should be justified because for all
other headings they are.

-- 
Max

Re: [PATCH v7 22/31] checkout: support checking out into a new working directory

[Junio C Hamano]

On Wed, Jul 16, 2014 at 9:19 PM, Max Kirillov <max@max630.net> wrote:
> Hi.
>
> On Sun, Jul 13, 2014 at 11:50:59AM +0700, Nguyễn Thái Ngọc Duy wrote:
>> +MULTIPLE CHECKOUT MODE
>> +-------------------------------
>
> This generates incorrect html for me, making all section
> until next heading "EXAMPLES" into a preformatted text. If I
> justify the line of dashes to be the exactly same width as
> header it starts generating correctly looking html.

Thanks; what you did is the correct AsciiDoc formatting.

Re: [PATCH v7 22/31] checkout: support checking out into a new working directory

[Eric Sunshine]

On Sun, Jul 13, 2014 at 12:50 AM, Nguyễn Thái Ngọc Duy
<pclouds@gmail.com> wrote:
> "git checkout --to" sets up a new working directory with a .git file
> pointing to $GIT_DIR/repos/<id>. It then executes "git checkout" again
> on the new worktree with the same arguments except "--to" is taken
> out. The second checkout execution, which is not contaminated with any
> info from the current repository, will actually check out and
> everything that normal "git checkout" does.
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
> diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
> index 0f341fc..543d874 100644
> --- a/Documentation/gitrepository-layout.txt
> +++ b/Documentation/gitrepository-layout.txt
> @@ -249,6 +249,13 @@ modules::
>         directory is ignored if $GIT_COMMON_DIR is set and
>         "$GIT_COMMON_DIR/modules" will be used instead.
>
> +repos::
> +       Contains worktree specific information of linked
> +       checkouts. Each subdirectory contains the worktree-related
> +       part of a linked checkout. This directory is ignored

s/ignored/ignored if/

> +       $GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/repos" will be
> +       used instead.
> +
>  SEE ALSO
>  --------
>  linkgit:git-init[1],

Re: [PATCH v7 25/31] prune: strategies for linked checkouts

[Thomas Rast]

Nguyễn Thái Ngọc Duy <pclouds@gmail.com> writes:

> (alias R=$GIT_COMMON_DIR/repos/<id>)
>
>  - linked checkouts are supposed to keep its location in $R/gitdir up
>    to date. The use case is auto fixup after a manual checkout move.
>
>  - linked checkouts are supposed to update mtime of $R/gitdir. If
>    $R/gitdir's mtime is older than a limit, and it points to nowhere,
>    repos/<id> is to be pruned.
>
>  - If $R/locked exists, repos/<id> is not supposed to be pruned. If
>    $R/locked exists and $R/gitdir's mtime is older than a really long
>    limit, warn about old unused repo.
>
>  - "git checkout --to" is supposed to make a hard link named $R/link
>    pointing to the .git file on supported file systems to help detect
>    the user manually deleting the checkout. If $R/link exists and its
>    link count is greated than 1, the repo is kept.
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  Documentation/git-prune.txt                |  3 +
>  Documentation/gitrepository-layout.txt     | 19 ++++++
>  builtin/checkout.c                         | 14 +++++
>  builtin/prune.c                            | 99 ++++++++++++++++++++++++++++++
>  setup.c                                    | 13 ++++
>  t/t2026-prune-linked-checkouts.sh (new +x) | 84 +++++++++++++++++++++++++

I get this from t2026.2 under valgrind:

  ==21334== Conditional jump or move depends on uninitialised value(s)
  ==21334==    at 0x46D49B: prune_repos_dir (prune.c:182)
  ==21334==    by 0x46D8C0: cmd_prune (prune.c:252)
  ==21334==    by 0x405C2F: run_builtin (git.c:351)
  ==21334==    by 0x405E47: handle_builtin (git.c:530)
  ==21334==    by 0x405F6B: run_argv (git.c:576)
  ==21334==    by 0x40610B: main (git.c:663)
  ==21334==  Uninitialised value was created by a stack allocation
  ==21334==    at 0x46D3BB: prune_repos_dir (prune.c:169)
  ==21334== 
  {
     <insert_a_suppression_name_here>
     Memcheck:Cond
     fun:prune_repos_dir
     fun:cmd_prune
     fun:run_builtin
     fun:handle_builtin
     fun:run_argv
     fun:main
  }
  not ok 2 - prune files inside $GIT_DIR/repos
  #
  #               mkdir .git/repos &&
  #               : >.git/repos/abc &&
  #               git prune --repos --verbose >actual &&
  #               cat >expect <<EOF &&
  #       Removing repos/abc: not a valid directory
  #       EOF
  #               test_i18ncmp expect actual &&
  #               ! test -f .git/repos/abc &&
  #               ! test -d .git/repos
  #

I think it's because of the early 'return 0' ...

> +static int prune_repo_dir(const char *id, struct stat *st, struct strbuf *reason)
> +{
> +	char *path;
> +	int fd, len;
> +
> +	if (!is_directory(git_path("repos/%s", id))) {
> +		strbuf_addf(reason, _("Removing repos/%s: not a valid directory"), id);
> +		return 1;
> +	}
> +	if (file_exists(git_path("repos/%s/locked", id)))
> +		return 0;

in this line, before the stat() actually runs, which then in the
condition ...

> +	if (stat(git_path("repos/%s/gitdir", id), st)) {
> +		st->st_mtime = expire;
> +		strbuf_addf(reason, _("Removing repos/%s: gitdir file does not exist"), id);
> +		return 1;
> +	}
[...]
> +}
> +
> +static void prune_repos_dir(void)
> +{
[...]
> +	struct stat st;
[...]
> +		if (!prune_repo_dir(d->d_name, &st, &reason) ||
> +		    st.st_mtime > expire)

causes the second arm to be evaluated when st.st_mtime is not
initialized yet.  Can you look into this?

-- 
Thomas Rast
tr@thomasrast.ch

Re: [PATCH v7 25/31] prune: strategies for linked checkouts

[Duy Nguyen]

On Sat, Jul 19, 2014 at 1:17 AM, Thomas Rast <tr@thomasrast.ch> wrote:
> I get this from t2026.2 under valgrind:
>
>   ==21334== Conditional jump or move depends on uninitialised value(s)
>   ==21334==    at 0x46D49B: prune_repos_dir (prune.c:182)
>   ==21334==    by 0x46D8C0: cmd_prune (prune.c:252)
>   ==21334==    by 0x405C2F: run_builtin (git.c:351)
>   ==21334==    by 0x405E47: handle_builtin (git.c:530)
>   ==21334==    by 0x405F6B: run_argv (git.c:576)
>   ==21334==    by 0x40610B: main (git.c:663)
>   ==21334==  Uninitialised value was created by a stack allocation
>   ==21334==    at 0x46D3BB: prune_repos_dir (prune.c:169)

Will fix. Thanks.
-- 
Duy

Re: [PATCH v7 23/31] checkout: clean up half-prepared directories in --to mode

[Eric Sunshine]

On Sun, Jul 13, 2014 at 12:51 AM, Nguyễn Thái Ngọc Duy
<pclouds@gmail.com> wrote:
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
>  builtin/checkout.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 47 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index 81adb74..3167fd2 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -20,6 +20,7 @@
>  #include "resolve-undo.h"
>  #include "submodule.h"
>  #include "argv-array.h"
> +#include "sigchain.h"
>
>  static const char * const checkout_usage[] = {
>         N_("git checkout [options] <branch>"),
> @@ -814,6 +815,35 @@ static int switch_branches(const struct checkout_opts *opts,
>         return ret || writeout_error;
>  }
>
> +static const char *junk_work_tree;
> +static const char *junk_git_dir;
> +static int is_junk;
> +static pid_t junk_pid;
> +
> +static void remove_junk(void)
> +{
> +       struct strbuf sb = STRBUF_INIT;
> +       if (!is_junk || getpid() != junk_pid)
> +               return;
> +       if (junk_git_dir) {
> +               strbuf_addstr(&sb, junk_git_dir);
> +               remove_dir_recursively(&sb, 0);
> +               strbuf_reset(&sb);
> +       }
> +       if (junk_work_tree) {
> +               strbuf_addstr(&sb, junk_work_tree);
> +               remove_dir_recursively(&sb, 0);
> +       }
> +       strbuf_release(&sb);
> +}
> +
> +static void remove_junk_on_signal(int signo)
> +{
> +       remove_junk();
> +       sigchain_pop(signo);
> +       raise(signo);
> +}
> +
>  static int prepare_linked_checkout(const struct checkout_opts *opts,
>                                    struct branch_info *new)
>  {
> @@ -822,7 +852,7 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
>         const char *path = opts->new_worktree, *name;
>         struct stat st;
>         struct child_process cp;
> -       int counter = 0, len;
> +       int counter = 0, len, ret;
>
>         if (!new->commit)
>                 die(_("no branch specified"));
> @@ -848,13 +878,21 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
>                 strbuf_addf(&sb_repo, "%d", counter);
>         }
>         name = strrchr(sb_repo.buf, '/') + 1;
> +
> +       junk_pid = getpid();
> +       atexit(remove_junk);
> +       sigchain_push_common(remove_junk_on_signal);
> +
>         if (mkdir(sb_repo.buf, 0777))
>                 die_errno(_("could not create directory of '%s'"), sb_repo.buf);
> +       junk_git_dir = sb_repo.buf;

I've managed to convince myself that, although junk_git_dir becomes a
dangling pointer by the end of prepare_linked_checkout(), it should
never afterward be accessed. Perhaps it would make sense to make this
easier to follow by clearing junk_git_dir when is_junk is cleared?

> +       is_junk = 1;
>
>         strbuf_addf(&sb_git, "%s/.git", path);
>         if (safe_create_leading_directories_const(sb_git.buf))
>                 die_errno(_("could not create leading directories of '%s'"),
>                           sb_git.buf);
> +       junk_work_tree = path;
>
>         write_file(sb_git.buf, 1, "gitdir: %s/repos/%s\n",
>                    real_path(get_git_common_dir()), name);
> @@ -879,7 +917,14 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
>         memset(&cp, 0, sizeof(cp));
>         cp.git_cmd = 1;
>         cp.argv = opts->saved_argv;
> -       return run_command(&cp);
> +       ret = run_command(&cp);
> +       if (!ret)
> +               is_junk = 0;

Here: perhaps also set is_junk_dir to NULL since it otherwise is about
to become a dangling pointer.

> +       strbuf_release(&sb);
> +       strbuf_release(&sb_repo);
> +       strbuf_release(&sb_git);
> +       return ret;
> +
>  }
>
>  static int git_checkout_config(const char *var, const char *value, void *cb)
> --
> 1.9.1.346.ga2b5940

Re: [PATCH v7 23/31] checkout: clean up half-prepared directories in --to mode

[Eric Sunshine]

On Sun, Jul 20, 2014 at 7:55 PM, Eric Sunshine <sunshine@sunshineco.com> wrote:
> On Sun, Jul 13, 2014 at 12:51 AM, Nguyễn Thái Ngọc Duy
> <pclouds@gmail.com> wrote:
>> +
>> +       junk_pid = getpid();
>> +       atexit(remove_junk);
>> +       sigchain_push_common(remove_junk_on_signal);
>> +
>>         if (mkdir(sb_repo.buf, 0777))
>>                 die_errno(_("could not create directory of '%s'"), sb_repo.buf);
>> +       junk_git_dir = sb_repo.buf;
>
> I've managed to convince myself that, although junk_git_dir becomes a
> dangling pointer by the end of prepare_linked_checkout(), it should
> never afterward be accessed. Perhaps it would make sense to make this
> easier to follow by clearing junk_git_dir when is_junk is cleared?
>
>> +       is_junk = 1;
>>
>>         strbuf_addf(&sb_git, "%s/.git", path);
>>         if (safe_create_leading_directories_const(sb_git.buf))
>>                 die_errno(_("could not create leading directories of '%s'"),
>>                           sb_git.buf);
>> +       junk_work_tree = path;
>>
>>         write_file(sb_git.buf, 1, "gitdir: %s/repos/%s\n",
>>                    real_path(get_git_common_dir()), name);
>> @@ -879,7 +917,14 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
>>         memset(&cp, 0, sizeof(cp));
>>         cp.git_cmd = 1;
>>         cp.argv = opts->saved_argv;
>> -       return run_command(&cp);
>> +       ret = run_command(&cp);
>> +       if (!ret)
>> +               is_junk = 0;
>
> Here: perhaps also set is_junk_dir to NULL since it otherwise is about
> to become a dangling pointer.

My bad: s/is_junk_dir/junk_git_dir/

Re: [PATCH v7 11/31] $GIT_COMMON_DIR: a new environment variable

[Eric Sunshine]

On Sun, Jul 13, 2014 at 12:50 AM, Nguyễn Thái Ngọc Duy
<pclouds@gmail.com> wrote:
> This variable is intended to support multiple working directories
> attached to a repository. Such a repository may have a main working
> directory, created by either "git init" or "git clone" and one or more
> linked working directories. These working directories and the main
> repository share the same repository directory.
>
> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
> diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
> index 17d2ea6..7629e38 100644
> --- a/Documentation/gitrepository-layout.txt
> +++ b/Documentation/gitrepository-layout.txt
> @@ -133,6 +138,11 @@ being a symref to point at the current branch.  Such a state
>  is often called 'detached HEAD.'  See linkgit:git-checkout[1]
>  for details.
>
> +config::
> +       Repository specific configuration file. This file is ignored

s/ignored/ignored if/

> +       $GIT_COMMON_DIR is set and "$GIT_COMMON_DIR/config" will be
> +       used instead.
> +
>  branches::
>         A slightly deprecated way to store shorthands to be used
>         to specify a URL to 'git fetch', 'git pull' and 'git push'.
> diff --git a/environment.c b/environment.c
> index fee12a6..6b74f68 100644
> --- a/environment.c
> +++ b/environment.c
> @@ -149,9 +149,18 @@ static void setup_git_env(void)
>                 git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
>         gitfile = read_gitfile(git_dir);
>         git_dir = xstrdup(gitfile ? gitfile : git_dir);
> -       git_object_dir = git_path_from_env(DB_ENVIRONMENT, "objects", &git_db_env);
> -       git_index_file = git_path_from_env(INDEX_ENVIRONMENT, "index", &git_index_env);
> -       git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, "info/grafts", &git_graft_env);
> +       git_common_dir = getenv(GIT_COMMON_DIR_ENVIRONMENT);
> +       if (git_common_dir) {
> +               git_common_dir_env = 1;
> +               git_common_dir = xstrdup(git_common_dir);
> +       } else
> +               git_common_dir = git_dir;
> +       git_object_dir = git_path_from_env(DB_ENVIRONMENT, git_common_dir,
> +                                          "objects", &git_db_env);
> +       git_index_file = git_path_from_env(INDEX_ENVIRONMENT, git_dir,
> +                                          "index", &git_index_env);
> +       git_graft_file = git_path_from_env(GRAFT_ENVIRONMENT, git_dir,
> +                                          "info/grafts", &git_graft_env);

Replacement refs come from git_common_dir, but grafts come from
git_dir. Is the inconsistency intentional?

>         if (getenv(NO_REPLACE_OBJECTS_ENVIRONMENT))
>                 check_replace_refs = 0;
>         namespace = expand_namespace(getenv(GIT_NAMESPACE_ENVIRONMENT));
> diff --git a/path.c b/path.c
> index 3deb80c..8a6586c 100644
> --- a/path.c
> +++ b/path.c
> @@ -90,6 +90,38 @@ static void replace_dir(struct strbuf *buf, int len, const char *newdir)
>                 buf->buf[newlen] = '/';
>  }
>
> +static const char *common_list[] = {
> +       "/branches", "/hooks", "/info", "/logs", "/lost-found", "/modules",
> +       "/objects", "/refs", "/remotes", "/rr-cache", "/svn",
> +       "config", "gc.pid", "packed-refs", "shallow",
> +       NULL
> +};
> +
> +static void update_common_dir(struct strbuf *buf, int git_dir_len)
> +{
> +       char *base = buf->buf + git_dir_len;
> +       const char **p;
> +
> +       if (is_dir_file(base, "logs", "HEAD"))
> +               return; /* keep this in $GIT_DIR */
> +       for (p = common_list; *p; p++) {
> +               const char *path = *p;
> +               int is_dir = 0;
> +               if (*path == '/') {
> +                       path++;
> +                       is_dir = 1;
> +               }
> +               if (is_dir && dir_prefix(base, path)) {
> +                       replace_dir(buf, git_dir_len, get_git_common_dir());
> +                       return;
> +               }
> +               if (!is_dir && !strcmp(base, path)) {
> +                       replace_dir(buf, git_dir_len, get_git_common_dir());
> +                       return;
> +               }

The bodies of these two conditionals are identical. Would it make
sense to combine them (or does a later patch take advantage of the
distinction)?

    if ((is_dir && dir_prefix(base, path)) ||
       (!is_dir && !strcmp(base, path))) {
        replace_dir(buf, git_dir_len, get_git_common_dir());
        return;
    }

> +       }
> +}
> +
>  static void adjust_git_path(struct strbuf *buf, int git_dir_len)
>  {
>         const char *base = buf->buf + git_dir_len;

Re: [PATCH v7 23/31] checkout: clean up half-prepared directories in --to mode

[Duy Nguyen]

On Mon, Jul 21, 2014 at 6:55 AM, Eric Sunshine <sunshine@sunshineco.com> wrote:
>> @@ -848,13 +878,21 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
>>                 strbuf_addf(&sb_repo, "%d", counter);
>>         }
>>         name = strrchr(sb_repo.buf, '/') + 1;
>> +
>> +       junk_pid = getpid();
>> +       atexit(remove_junk);
>> +       sigchain_push_common(remove_junk_on_signal);
>> +
>>         if (mkdir(sb_repo.buf, 0777))
>>                 die_errno(_("could not create directory of '%s'"), sb_repo.buf);
>> +       junk_git_dir = sb_repo.buf;
>
> I've managed to convince myself that, although junk_git_dir becomes a
> dangling pointer by the end of prepare_linked_checkout(), it should
> never afterward be accessed. Perhaps it would make sense to make this
> easier to follow by clearing junk_git_dir when is_junk is cleared?

You're right. And the dangling junk_git_dir can be accessed if "ret"
below is non-zero. Will strdup() both junk_*_dir and free them in "if
(!ret)" block. Thanks for catching.

>> @@ -879,7 +917,14 @@ static int prepare_linked_checkout(const struct checkout_opts *opts,
>>         memset(&cp, 0, sizeof(cp));
>>         cp.git_cmd = 1;
>>         cp.argv = opts->saved_argv;
>> -       return run_command(&cp);
>> +       ret = run_command(&cp);
>> +       if (!ret)
>> +               is_junk = 0;
>
> Here: perhaps also set is_junk_dir to NULL since it otherwise is about
> to become a dangling pointer.
>
>> +       strbuf_release(&sb);
>> +       strbuf_release(&sb_repo);
>> +       strbuf_release(&sb_git);
>> +       return ret;
-- 
Duy