[PATCH v5 1/2] worktrees: add find_shared_symref

[PATCH v5 1/2] worktrees: add find_shared_symref

[David Turner]

Add a new function, find_shared_symref, which contains the heart of
die_if_checked_out, but works for any symref, not just HEAD.  Refactor
die_if_checked_out to use the same infrastructure as
find_shared_symref.

Soon, we will use find_shared_symref to protect notes merges in
worktrees.

Signed-off-by: David Turner <dturner@twopensource.com>
---

This reroll fixes issues reported by Eric Sunshine: leaks
and Johan Herland: prepositions and broken &&

---
 branch.c | 45 ++++++++++++++++++++++++++++++++++-----------
 branch.h |  8 ++++++++
 2 files changed, 42 insertions(+), 11 deletions(-)

diff --git a/branch.c b/branch.c
index c85be07..d2b3586 100644
--- a/branch.c
+++ b/branch.c
@@ -311,21 +311,22 @@ void remove_branch_state(void)
 	unlink(git_path("SQUASH_MSG"));
 }
 
-static void check_linked_checkout(const char *branch, const char *id)
+static char *find_linked_symref(const char *symref, const char *branch,
+				const char *id)
 {
 	struct strbuf sb = STRBUF_INIT;
 	struct strbuf path = STRBUF_INIT;
 	struct strbuf gitdir = STRBUF_INIT;
 
 	/*
-	 * $GIT_COMMON_DIR/HEAD is practically outside
-	 * $GIT_DIR so resolve_ref_unsafe() won't work (it
-	 * uses git_path). Parse the ref ourselves.
+	 * $GIT_COMMON_DIR/$symref (e.g. HEAD) is practically outside
+	 * $GIT_DIR so resolve_ref_unsafe() won't work (it uses
+	 * git_path). Parse the ref ourselves.
 	 */
 	if (id)
-		strbuf_addf(&path, "%s/worktrees/%s/HEAD", get_git_common_dir(), id);
+		strbuf_addf(&path, "%s/worktrees/%s/%s", get_git_common_dir(), id, symref);
 	else
-		strbuf_addf(&path, "%s/HEAD", get_git_common_dir());
+		strbuf_addf(&path, "%s/%s", get_git_common_dir(), symref);
 
 	if (!strbuf_readlink(&sb, path.buf, 0)) {
 		if (!starts_with(sb.buf, "refs/") ||
@@ -349,31 +350,53 @@ static void check_linked_checkout(const char *branch, const char *id)
 		strbuf_addstr(&gitdir, get_git_common_dir());
 	skip_prefix(branch, "refs/heads/", &branch);
 	strbuf_strip_suffix(&gitdir, ".git");
-	die(_("'%s' is already checked out at '%s'"), branch, gitdir.buf);
+
+	strbuf_release(&path);
+	strbuf_release(&sb);
+	return strbuf_detach(&gitdir, NULL);
 done:
 	strbuf_release(&path);
 	strbuf_release(&sb);
 	strbuf_release(&gitdir);
+
+	return NULL;
 }
 
-void die_if_checked_out(const char *branch)
+char *find_shared_symref(const char *symref, const char *target)
 {
 	struct strbuf path = STRBUF_INIT;
 	DIR *dir;
 	struct dirent *d;
+	char *existing;
 
-	check_linked_checkout(branch, NULL);
+	if ((existing = find_linked_symref(symref, target, NULL)))
+		return existing;
 
 	strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
 	dir = opendir(path.buf);
 	strbuf_release(&path);
 	if (!dir)
-		return;
+		return NULL;
 
 	while ((d = readdir(dir)) != NULL) {
 		if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
 			continue;
-		check_linked_checkout(branch, d->d_name);
+		existing = find_linked_symref(symref, target, d->d_name);
+		if (existing) {
+			closedir(dir);
+			return existing;
+		}
 	}
 	closedir(dir);
+
+	return NULL;
+}
+
+void die_if_checked_out(const char *branch)
+{
+	char *existing;
+
+	existing = find_shared_symref("HEAD", branch);
+	if (existing)
+		die(_("'%s' is already checked out at '%s'"), branch, existing);
 }
diff --git a/branch.h b/branch.h
index 58aa45f..d3446ed 100644
--- a/branch.h
+++ b/branch.h
@@ -59,4 +59,12 @@ extern int read_branch_desc(struct strbuf *, const char *branch_name);
  */
 extern void die_if_checked_out(const char *branch);
 
+/*
+ * Check if a per-worktree symref points to a ref in the main worktree
+ * or any linked worktree, and return the path to the exising worktree
+ * if it is.  Returns NULL if there is no existing ref.  The caller is
+ * responsible for freeing the returned path.
+ */
+extern char *find_shared_symref(const char *symref, const char *target);
+
 #endif
-- 
2.0.4.315.gad8727a-twtrsrc

[PATCH v5 2/2] notes: handle multiple worktrees

[David Turner]

Before creating NOTES_MERGE_REF, check NOTES_MERGE_REF using
find_shared_symref and die if we find one.  This prevents simultaneous
merges to the same notes branch from different worktrees.

Signed-off-by: David Turner <dturner@twopensource.com>
---
 builtin/notes.c                  |  6 ++++
 t/t3320-notes-merge-worktrees.sh | 72 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100755 t/t3320-notes-merge-worktrees.sh

diff --git a/builtin/notes.c b/builtin/notes.c
index 63f95fc..0423480 100644
--- a/builtin/notes.c
+++ b/builtin/notes.c
@@ -19,6 +19,7 @@
 #include "string-list.h"
 #include "notes-merge.h"
 #include "notes-utils.h"
+#include "branch.h"
 
 static const char * const git_notes_usage[] = {
 	N_("git notes [--ref <notes-ref>] [list [<object>]]"),
@@ -825,10 +826,15 @@ static int merge(int argc, const char **argv, const char *prefix)
 		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
 			   0, UPDATE_REFS_DIE_ON_ERR);
 	else { /* Merge has unresolved conflicts */
+		char *existing;
 		/* Update .git/NOTES_MERGE_PARTIAL with partial merge result */
 		update_ref(msg.buf, "NOTES_MERGE_PARTIAL", result_sha1, NULL,
 			   0, UPDATE_REFS_DIE_ON_ERR);
 		/* Store ref-to-be-updated into .git/NOTES_MERGE_REF */
+		existing = find_shared_symref("NOTES_MERGE_REF", default_notes_ref());
+		if (existing)
+			die(_("A notes merge into %s is already in-progress at %s"),
+			    default_notes_ref(), existing);
 		if (create_symref("NOTES_MERGE_REF", default_notes_ref(), NULL))
 			die("Failed to store link to current notes ref (%s)",
 			    default_notes_ref());
diff --git a/t/t3320-notes-merge-worktrees.sh b/t/t3320-notes-merge-worktrees.sh
new file mode 100755
index 0000000..a7beef2
--- /dev/null
+++ b/t/t3320-notes-merge-worktrees.sh
@@ -0,0 +1,72 @@
+#!/bin/sh
+#
+# Copyright (c) 2015 Twitter, Inc
+#
+
+test_description='Test merging of notes trees in multiple worktrees'
+
+. ./test-lib.sh
+
+test_expect_success 'setup commit' '
+	test_commit tantrum
+'
+
+commit_tantrum=$(git rev-parse tantrum^{commit})
+
+test_expect_success 'setup notes ref (x)' '
+	git config core.notesRef refs/notes/x &&
+	git notes add -m "x notes on tantrum" tantrum
+'
+
+test_expect_success 'setup local branch (y)' '
+	git update-ref refs/notes/y refs/notes/x &&
+	git config core.notesRef refs/notes/y &&
+	git notes remove tantrum
+'
+
+test_expect_success 'setup remote branch (z)' '
+	git update-ref refs/notes/z refs/notes/x &&
+	git config core.notesRef refs/notes/z &&
+	git notes add -f -m "conflicting notes on tantrum" tantrum
+'
+
+test_expect_success 'modify notes ref ourselves (x)' '
+	git config core.notesRef refs/notes/x &&
+	git notes add -f -m "more conflicting notes on tantrum" tantrum
+'
+
+test_expect_success 'create some new worktrees' '
+	git worktree add -b newbranch worktree master &&
+	git worktree add -b newbranch2 worktree2 master
+'
+
+test_expect_success 'merge z into y fails and sets NOTES_MERGE_REF' '
+	git config core.notesRef refs/notes/y &&
+	test_must_fail git notes merge z &&
+	echo "ref: refs/notes/y" > expect &&
+	test_cmp .git/NOTES_MERGE_REF expect
+'
+
+test_expect_success 'merge z into y while mid-merge in another workdir fails' '
+	(
+		cd worktree &&
+		git config core.notesRef refs/notes/y &&
+		test_must_fail git notes merge z 2>err &&
+		grep "A notes merge into refs/notes/y is already in-progress at" err
+	) &&
+	test_path_is_missing .git/worktrees/worktree/NOTES_MERGE_REF
+'
+
+test_expect_success 'merge z into x while mid-merge on y succeeds' '
+	(
+		cd worktree2 &&
+		git config core.notesRef refs/notes/x &&
+		test_must_fail git notes merge z 2>&1 >out &&
+		grep "Automatic notes merge failed" out &&
+		grep -v "A notes merge into refs/notes/x is already in-progress in" out
+	) &&
+	echo "ref: refs/notes/x" > expect &&
+	test_cmp .git/worktrees/worktree2/NOTES_MERGE_REF expect
+'
+
+test_done
-- 
2.0.4.315.gad8727a-twtrsrc

Re: [PATCH v5 1/2] worktrees: add find_shared_symref

[Eric Sunshine]

On Mon, Aug 3, 2015 at 2:48 PM, David Turner <dturner@twopensource.com> wrote:
> Add a new function, find_shared_symref, which contains the heart of
> die_if_checked_out, but works for any symref, not just HEAD.  Refactor
> die_if_checked_out to use the same infrastructure as
> find_shared_symref.
>
> Soon, we will use find_shared_symref to protect notes merges in
> worktrees.

A couple comments below. The first may be worth a re-roll; the second
is more a taste thing. Neither is blocking if you don't happen to
re-roll.

> Signed-off-by: David Turner <dturner@twopensource.com>
> ---
> diff --git a/branch.c b/branch.c
> index c85be07..d2b3586 100644
> --- a/branch.c
> +++ b/branch.c
> @@ -349,31 +350,53 @@ static void check_linked_checkout(const char *branch, const char *id)
>                 strbuf_addstr(&gitdir, get_git_common_dir());
>         skip_prefix(branch, "refs/heads/", &branch);
>         strbuf_strip_suffix(&gitdir, ".git");
> -       die(_("'%s' is already checked out at '%s'"), branch, gitdir.buf);
> +
> +       strbuf_release(&path);
> +       strbuf_release(&sb);
> +       return strbuf_detach(&gitdir, NULL);
>  done:
>         strbuf_release(&path);
>         strbuf_release(&sb);
>         strbuf_release(&gitdir);
> +
> +       return NULL;
>  }

This would be cleaner and less redundant if you assign the existing
location to a variable and just fall through to the 'done' label:

    char *existing = NULL;
    ...
        skip_prefix(branch, "refs/heads/", &branch);
        strbuf_strip_suffix(&gitdir, ".git");
        existing = strbuf_detach(&gitdir, NULL);
    done:
        strbuf_release(&path);
        strbuf_release(&sb);
        strbuf_release(&gitdir);
        return existing;

There's no worry that the "existing" path will be clobbered by
strbuf_release(&gitdir) since it's been detached already (and it's
safe to release the strbuf without affecting what has been detached
from it).

> -void die_if_checked_out(const char *branch)
> +char *find_shared_symref(const char *symref, const char *target)
>  {
>         struct strbuf path = STRBUF_INIT;
>         DIR *dir;
>         struct dirent *d;
> +       char *existing;
>
> -       check_linked_checkout(branch, NULL);
> +       if ((existing = find_linked_symref(symref, target, NULL)))
> +               return existing;
>
>         strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
>         dir = opendir(path.buf);
>         strbuf_release(&path);
>         if (!dir)
> -               return;
> +               return NULL;
>
>         while ((d = readdir(dir)) != NULL) {
>                 if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
>                         continue;
> -               check_linked_checkout(branch, d->d_name);
> +               existing = find_linked_symref(symref, target, d->d_name);
> +               if (existing) {
> +                       closedir(dir);
> +                       return existing;

For consistency with code nearby, this could have been handled by
adding a 'done' label above the closedir() below and jumping to it
from here, and then 'return existing'.

> +               }
>         }
>         closedir(dir);
> +
> +       return NULL;
> +}
> +
> +void die_if_checked_out(const char *branch)
> +{
> +       char *existing;
> +
> +       existing = find_shared_symref("HEAD", branch);
> +       if (existing)
> +               die(_("'%s' is already checked out at '%s'"), branch, existing);
>  }

Re: [PATCH v5 1/2] worktrees: add find_shared_symref

[Eric Sunshine]

On Mon, Aug 3, 2015 at 7:06 PM, Eric Sunshine <sunshine@sunshineco.com> wrote:
> On Mon, Aug 3, 2015 at 2:48 PM, David Turner <dturner@twopensource.com> wrote:
>> Add a new function, find_shared_symref, which contains the heart of
>> die_if_checked_out, but works for any symref, not just HEAD.  Refactor
>> die_if_checked_out to use the same infrastructure as
>> find_shared_symref.
>>
>> Soon, we will use find_shared_symref to protect notes merges in
>> worktrees.
>>
>> Signed-off-by: David Turner <dturner@twopensource.com>
>> ---
>> diff --git a/branch.c b/branch.c
>> index c85be07..d2b3586 100644
>> --- a/branch.c
>> +++ b/branch.c
>> @@ -349,31 +350,53 @@ static void check_linked_checkout(const char *branch, const char *id)
>>                 strbuf_addstr(&gitdir, get_git_common_dir());
>>         skip_prefix(branch, "refs/heads/", &branch);
>>         strbuf_strip_suffix(&gitdir, ".git");
>> -       die(_("'%s' is already checked out at '%s'"), branch, gitdir.buf);

In addition to the other issues already mentioned, this one is a bit
more serious (though still rather superficial):

With this change, the skip_prefix(branch, "refs/heads/", &branch)
becomes meaningless. It was used by the die() to provide a nicer
looking error message, however, 'branch' now is never used after
skip_prefix(). More below...

>> +
>> +       strbuf_release(&path);
>> +       strbuf_release(&sb);
>> +       return strbuf_detach(&gitdir, NULL);
>>  done:
>>         strbuf_release(&path);
>>         strbuf_release(&sb);
>>         strbuf_release(&gitdir);
>> +
>> +       return NULL;
>>  }
>
> This would be cleaner and less redundant if you assign the existing
> location to a variable and just fall through to the 'done' label:
>
>     char *existing = NULL;
>     ...
>         skip_prefix(branch, "refs/heads/", &branch);
>         strbuf_strip_suffix(&gitdir, ".git");
>         existing = strbuf_detach(&gitdir, NULL);
>     done:
>         strbuf_release(&path);
>         strbuf_release(&sb);
>         strbuf_release(&gitdir);
>         return existing;
>
> There's no worry that the "existing" path will be clobbered by
> strbuf_release(&gitdir) since it's been detached already (and it's
> safe to release the strbuf without affecting what has been detached
> from it).
>
>> -void die_if_checked_out(const char *branch)
>> +char *find_shared_symref(const char *symref, const char *target)
>>  {
>>         struct strbuf path = STRBUF_INIT;
>>         DIR *dir;
>>         struct dirent *d;
>> +       char *existing;
>>
>> -       check_linked_checkout(branch, NULL);
>> +       if ((existing = find_linked_symref(symref, target, NULL)))
>> +               return existing;
>>
>>         strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
>>         dir = opendir(path.buf);
>>         strbuf_release(&path);
>>         if (!dir)
>> -               return;
>> +               return NULL;
>>
>>         while ((d = readdir(dir)) != NULL) {
>>                 if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
>>                         continue;
>> -               check_linked_checkout(branch, d->d_name);
>> +               existing = find_linked_symref(symref, target, d->d_name);
>> +               if (existing) {
>> +                       closedir(dir);
>> +                       return existing;
>
> For consistency with code nearby, this could have been handled by
> adding a 'done' label above the closedir() below and jumping to it
> from here, and then 'return existing'.
>
>> +               }
>>         }
>>         closedir(dir);
>> +
>> +       return NULL;
>> +}
>> +
>> +void die_if_checked_out(const char *branch)
>> +{
>> +       char *existing;
>> +
>> +       existing = find_shared_symref("HEAD", branch);
>> +       if (existing)
>> +               die(_("'%s' is already checked out at '%s'"), branch, existing);

Unlike the original die() in check_linked_checkout() which printed the
branch named shortened by skip_prefix(), this one still prints the
long-form branch name. An easy fix would be to move the skip_prefix()
invocation down to here to skip the "refs/heads/" prefix just before
die().

>>  }