[PATCH v3 00/19] "git apply --3way"

[PATCH v3 00/19] "git apply --3way"

[Junio C Hamano]

Here is the third round.  Previous ones are:

    http://thread.gmane.org/gmane.comp.version-control.git/197538
    http://thread.gmane.org/gmane.comp.version-control.git/197637

"git am -3" is useful when you have to accept a patch submission to
a tree that has slightly been modified, but when you are reordeing
your own work, you would be picking some parts of a later commits to
earlier codebase without wanting to make commits out of individual
steps.

Teach "git apply" a similar "-3"way merge fallback option with this
series, and you can now apply your patches without having to reduce
context.  As it will leave the conflicted halves in the index and
let you manually resolve conflicts in the working tree, "--3way"
implies "--index", and cannot be used with "--cached".

Note that this does not call merge-recursive like "am -3" does, and
does not implement renames (i.e. a patch wants to modify path A,
your codebase has the corresponding contents at path B---"git am -3"
will end up modifying path B, but the round of this series does
not).  It should be more or less straightforward to enhance it,
though.  Instead of aborting with "preimage A does not exist in the
index nor the working tree", after finding the necessary blob that
the patch author had at path A, you run the similarity algorithm
with the blob in your tree to find path B, update the "struct patch"
to rewrite it to apply to path B, and let the existing code take
care of the rest.

Given that I started this early last month, even discounting the
fact that I was looking at it only in the background, the whole
thing would have been a bit too big for a student inexperienced to
the code base to swallow.  I would say that it would be a good
bite-sized GSoC project next summer to build on this series and make
it replace the "am -3" implementation (that means the above "apply a
patch to A to path B" needs to be added), which lets us kill the
ugly "--build-fake-ancestor" hack.

Junio C Hamano (19):
  apply: fix an incomplete comment in check_patch()
  apply: a bit more comments on PATH_TO_BE_DELETED
  apply: clear_image() clears things a bit more
  apply: refactor read_file_or_gitlink()
  apply: factor out checkout_target() helper function
  apply: split load_preimage() helper function out
  apply: refactor "previous patch" logic
  apply: further split load_preimage()
  apply: move check_to_create_blob() closer to its sole caller
  apply: move "already exists" logic to check_to_create()
  apply: accept -3/--3way command line option
  apply: fall back on three-way merge
  apply: plug the three-way merge logic in
  apply: move verify_index_match() higher
  apply: --3way with add/add conflict
  apply: register conflicted stages to the index
  apply: allow rerere() upon --3way results
  apply: document --3way option
  apply --3way: tests

 Documentation/git-apply.txt |  11 +-
 builtin/apply.c             | 550 ++++++++++++++++++++++++++++++++++----------
 t/t4108-apply-threeway.sh   | 157 +++++++++++++
 t/t4117-apply-reject.sh     |   8 +
 4 files changed, 608 insertions(+), 118 deletions(-)
 create mode 100755 t/t4108-apply-threeway.sh

-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 01/19] apply: fix an incomplete comment in check_patch()

[Junio C Hamano]

This check is not only about type-change (for which it would be
sufficient to check only was_deleted()) but is also about a swap
rename.  Otherwise to_be_deleted() check is not justified.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 725712d..be4e3f3 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3218,16 +3218,22 @@ static int check_patch(struct patch *patch)
 		return status;
 	old_name = patch->old_name;
 
+	/*
+	 * A type-change diff is always split into a patch to
+	 * delete old, immediately followed by a patch to
+	 * create new (see diff.c::run_diff()); in such a case
+	 * it is Ok that the entry to be deleted by the
+	 * previous patch is still in the working tree and in
+	 * the index.
+	 *
+	 * A patch to swap-rename between A and B would first rename
+	 * A to B and then rename B to A.  While applying the first
+	 * one, the presense of B should not stop A from renamed to B,
+	 * as to_be_deleted() knows about the later rename.  Removal
+	 * of B and rename from A to B will be handle the same way.
+	 */
 	if ((tpatch = in_fn_table(new_name)) &&
-			(was_deleted(tpatch) || to_be_deleted(tpatch)))
-		/*
-		 * A type-change diff is always split into a patch to
-		 * delete old, immediately followed by a patch to
-		 * create new (see diff.c::run_diff()); in such a case
-		 * it is Ok that the entry to be deleted by the
-		 * previous patch is still in the working tree and in
-		 * the index.
-		 */
+	    (was_deleted(tpatch) || to_be_deleted(tpatch)))
 		ok_if_exists = 1;
 	else
 		ok_if_exists = 0;
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 02/19] apply: a bit more comments on PATH_TO_BE_DELETED

[Junio C Hamano]

The code is littered with to_be_deleted() whose purpose is not so clear.
Describe where it matters.  Also remove an extra space before "#define"
that snuck in by mistake at 7fac0ee (builtin-apply: keep information about
files to be deleted, 2009-04-11).

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index be4e3f3..8488c8e 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -2970,9 +2970,15 @@ static struct patch *in_fn_table(const char *name)
  * item->util in the filename table records the status of the path.
  * Usually it points at a patch (whose result records the contents
  * of it after applying it), but it could be PATH_WAS_DELETED for a
- * path that a previously applied patch has already removed.
+ * path that a previously applied patch has already removed, or
+ * PATH_TO_BE_DELETED for a path that a later patch would remove.
+ *
+ * The latter is needed to deal with a case where two paths A and B
+ * are swapped by first renaming A to B and then renaming B to A;
+ * moving A to B should not be prevented due to presense of B as we
+ * will remove it in a later patch.
  */
- #define PATH_TO_BE_DELETED ((struct patch *) -2)
+#define PATH_TO_BE_DELETED ((struct patch *) -2)
 #define PATH_WAS_DELETED ((struct patch *) -1)
 
 static int to_be_deleted(struct patch *patch)
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 03/19] apply: clear_image() clears things a bit more

[Junio C Hamano]

The clear_image() function did not clear the line table in the image
structure; this does not matter for the current callers, as the function
is only called from the codepaths that deal with binary patches where the
line table is never populated, and the codepaths that do populate the line
table free it themselves.

But it will start to matter when we introduce a codepath to retry a failed
patch, so make sure it clears and frees everything.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 8488c8e..e2b0942 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -371,8 +371,8 @@ static void prepare_image(struct image *image, char *buf, size_t len,
 static void clear_image(struct image *image)
 {
 	free(image->buf);
-	image->buf = NULL;
-	image->len = 0;
+	free(image->line_allocated);
+	memset(image, 0, sizeof(*image));
 }
 
 /* fmt must contain _one_ %s and no other substitution */
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 04/19] apply: refactor read_file_or_gitlink()

[Junio C Hamano]

Reading a blob out of the object store does not have to require that the
caller has a cache entry for it.

Create a read_blob_object() helper function that takes the object name and
mode, and use it to reimplement the original function as a thin wrapper to
it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index e2b0942..3199691 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -2930,20 +2930,17 @@ static int apply_fragments(struct image *img, struct patch *patch)
 	return 0;
 }
 
-static int read_file_or_gitlink(struct cache_entry *ce, struct strbuf *buf)
+static int read_blob_object(struct strbuf *buf, const unsigned char *sha1, unsigned mode)
 {
-	if (!ce)
-		return 0;
-
-	if (S_ISGITLINK(ce->ce_mode)) {
+	if (S_ISGITLINK(mode)) {
 		strbuf_grow(buf, 100);
-		strbuf_addf(buf, "Subproject commit %s\n", sha1_to_hex(ce->sha1));
+		strbuf_addf(buf, "Subproject commit %s\n", sha1_to_hex(sha1));
 	} else {
 		enum object_type type;
 		unsigned long sz;
 		char *result;
 
-		result = read_sha1_file(ce->sha1, &type, &sz);
+		result = read_sha1_file(sha1, &type, &sz);
 		if (!result)
 			return -1;
 		/* XXX read_sha1_file NUL-terminates */
@@ -2952,6 +2949,13 @@ static int read_file_or_gitlink(struct cache_entry *ce, struct strbuf *buf)
 	return 0;
 }
 
+static int read_file_or_gitlink(struct cache_entry *ce, struct strbuf *buf)
+{
+	if (!ce)
+		return 0;
+	return read_blob_object(buf, ce->sha1, ce->ce_mode);
+}
+
 static struct patch *in_fn_table(const char *name)
 {
 	struct string_list_item *item;
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 05/19] apply: factor out checkout_target() helper function

[Junio C Hamano]

When a patch wants to touch a path, if the path exists in the index
but is missing in the working tree, "git apply --index" checks out
the file to the working tree from the index automatically and then
applies the patch.

Split this logic out to a separate helper function.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 3199691..6a1fdc0 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3034,6 +3034,18 @@ static void prepare_fn_table(struct patch *patch)
 	}
 }
 
+static int checkout_target(struct cache_entry *ce, struct stat *st)
+{
+	struct checkout costate;
+
+	memset(&costate, 0, sizeof(costate));
+	costate.base_dir = "";
+	costate.refresh_cache = 1;
+	if (checkout_entry(ce, &costate, NULL) || lstat(ce->name, st))
+		return error(_("cannot checkout %s"), ce->name);
+	return 0;
+}
+
 static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *ce)
 {
 	struct strbuf buf = STRBUF_INIT;
@@ -3163,13 +3175,7 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
 		}
 		*ce = active_cache[pos];
 		if (stat_ret < 0) {
-			struct checkout costate;
-			/* checkout */
-			memset(&costate, 0, sizeof(costate));
-			costate.base_dir = "";
-			costate.refresh_cache = 1;
-			if (checkout_entry(*ce, &costate, NULL) ||
-			    lstat(old_name, st))
+			if (checkout_target(*ce, st))
 				return -1;
 		}
 		if (!cached && verify_index_match(*ce, st))
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 06/19] apply: split load_preimage() helper function out

[Junio C Hamano]

The function apply_data() gets a patch for a single path, reads the
preimage in core, and applies the change represented in the patch.

Separate out the first part that reads the preimage into a separate
helper function load_preimage().

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 6a1fdc0..8496db5 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3046,10 +3046,10 @@ static int checkout_target(struct cache_entry *ce, struct stat *st)
 	return 0;
 }
 
-static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *ce)
+static int load_preimage(struct image *image,
+			 struct patch *patch, struct stat *st, struct cache_entry *ce)
 {
 	struct strbuf buf = STRBUF_INIT;
-	struct image image;
 	size_t len;
 	char *img;
 	struct patch *tpatch;
@@ -3086,7 +3086,16 @@ static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *
 	}
 
 	img = strbuf_detach(&buf, &len);
-	prepare_image(&image, img, len, !patch->is_binary);
+	prepare_image(image, img, len, !patch->is_binary);
+	return 0;
+}
+
+static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *ce)
+{
+	struct image image;
+
+	if (load_preimage(&image, patch, st, ce) < 0)
+		return -1;
 
 	if (apply_fragments(&image, patch) < 0)
 		return -1; /* note with --reject this succeeds. */
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 07/19] apply: refactor "previous patch" logic

[Junio C Hamano]

The code to grab the result of application of a previous patch in the
input was mixed with error message generation for a case where a later
patch tries to modify contents of a path that has been removed.

The same code is duplicated elsewhere in the code.  Introduce a helper
to clarify what is going on.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 76 +++++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 50 insertions(+), 26 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 8496db5..78dc1a8 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3046,22 +3046,50 @@ static int checkout_target(struct cache_entry *ce, struct stat *st)
 	return 0;
 }
 
+static struct patch *previous_patch(struct patch *patch, int *gone)
+{
+	struct patch *previous;
+
+	*gone = 0;
+	if (patch->is_copy || patch->is_rename)
+		return NULL; /* "git" patches do not depend on the order */
+
+	previous = in_fn_table(patch->old_name);
+	if (!previous)
+		return NULL;
+
+	if (to_be_deleted(previous))
+		return NULL; /* the deletion hasn't happened yet */
+
+	if (was_deleted(previous))
+		*gone = 1;
+
+	return previous;
+}
+
+/*
+ * We are about to apply "patch"; populate the "image" with the
+ * current version we have, from the working tree or from the index,
+ * depending on the situation e.g. --cached/--index.  If we are
+ * applying a non-git patch that incrementally updates the tree,
+ * we read from the result of a previous diff.
+ */
 static int load_preimage(struct image *image,
 			 struct patch *patch, struct stat *st, struct cache_entry *ce)
 {
 	struct strbuf buf = STRBUF_INIT;
 	size_t len;
 	char *img;
-	struct patch *tpatch;
+	struct patch *previous;
+	int status;
 
-	if (!(patch->is_copy || patch->is_rename) &&
-	    (tpatch = in_fn_table(patch->old_name)) != NULL && !to_be_deleted(tpatch)) {
-		if (was_deleted(tpatch)) {
-			return error(_("patch %s has been renamed/deleted"),
-				patch->old_name);
-		}
+	previous = previous_patch(patch, &status);
+	if (status)
+		return error(_("path %s has been renamed/deleted"),
+			     patch->old_name);
+	if (previous) {
 		/* We have a patched copy in memory; use that. */
-		strbuf_add(&buf, tpatch->result, tpatch->resultsize);
+		strbuf_add(&buf, previous->result, previous->resultsize);
 	} else if (cached) {
 		if (read_file_or_gitlink(ce, &buf))
 			return error(_("read of %s failed"), patch->old_name);
@@ -3143,39 +3171,35 @@ static int verify_index_match(struct cache_entry *ce, struct stat *st)
 	return ce_match_stat(ce, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
 }
 
+/*
+ * If "patch" that we are looking at modifies or deletes what we have,
+ * we would want it not to lose any local modification we have, either
+ * in the working tree or in the index.
+ */
 static int check_preimage(struct patch *patch, struct cache_entry **ce, struct stat *st)
 {
 	const char *old_name = patch->old_name;
-	struct patch *tpatch = NULL;
-	int stat_ret = 0;
+	struct patch *previous = NULL;
+	int stat_ret = 0, status;
 	unsigned st_mode = 0;
 
-	/*
-	 * Make sure that we do not have local modifications from the
-	 * index when we are looking at the index.  Also make sure
-	 * we have the preimage file to be patched in the work tree,
-	 * unless --cached, which tells git to apply only in the index.
-	 */
 	if (!old_name)
 		return 0;
 
 	assert(patch->is_new <= 0);
+	previous = previous_patch(patch, &status);
 
-	if (!(patch->is_copy || patch->is_rename) &&
-	    (tpatch = in_fn_table(old_name)) != NULL && !to_be_deleted(tpatch)) {
-		if (was_deleted(tpatch))
-			return error(_("%s: has been deleted/renamed"), old_name);
-		st_mode = tpatch->new_mode;
+	if (status)
+		return error(_("path %s has been renamed/deleted"), old_name);
+	if (previous) {
+		st_mode = previous->new_mode;
 	} else if (!cached) {
 		stat_ret = lstat(old_name, st);
 		if (stat_ret && errno != ENOENT)
 			return error(_("%s: %s"), old_name, strerror(errno));
 	}
 
-	if (to_be_deleted(tpatch))
-		tpatch = NULL;
-
-	if (check_index && !tpatch) {
+	if (check_index && !previous) {
 		int pos = cache_name_pos(old_name, strlen(old_name));
 		if (pos < 0) {
 			if (patch->is_new < 0)
@@ -3197,7 +3221,7 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
 		return error(_("%s: %s"), old_name, strerror(errno));
 	}
 
-	if (!cached && !tpatch)
+	if (!cached && !previous)
 		st_mode = ce_mode_from_stat(*ce, st->st_mode);
 
 	if (patch->is_new < 0)
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 08/19] apply: further split load_preimage()

[Junio C Hamano]

load_preimage() is very specific to grab the current contents for
the path given by patch->old_name.  Split the logic that grabs the
contents for a path out of it into a separate load_patch_target()
function.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 59 ++++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 40 insertions(+), 19 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 78dc1a8..35e9a9c 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3067,6 +3067,31 @@ static struct patch *previous_patch(struct patch *patch, int *gone)
 	return previous;
 }
 
+#define SUBMODULE_PATCH_WITHOUT_INDEX 1
+
+static int load_patch_target(struct strbuf *buf,
+			     struct cache_entry *ce,
+			     struct stat *st,
+			     const char *name,
+			     unsigned expected_mode)
+{
+	if (cached) {
+		if (read_file_or_gitlink(ce, buf))
+			return error(_("read of %s failed"), name);
+	} else if (name) {
+		if (S_ISGITLINK(expected_mode)) {
+			if (ce)
+				return read_file_or_gitlink(ce, buf);
+			else
+				return SUBMODULE_PATCH_WITHOUT_INDEX;
+		} else {
+			if (read_old_data(st, name, buf))
+				return error(_("read of %s failed"), name);
+		}
+	}
+	return 0;
+}
+
 /*
  * We are about to apply "patch"; populate the "image" with the
  * current version we have, from the working tree or from the index,
@@ -3090,26 +3115,22 @@ static int load_preimage(struct image *image,
 	if (previous) {
 		/* We have a patched copy in memory; use that. */
 		strbuf_add(&buf, previous->result, previous->resultsize);
-	} else if (cached) {
-		if (read_file_or_gitlink(ce, &buf))
+	} else {
+		status = load_patch_target(&buf, ce, st,
+					   patch->old_name, patch->old_mode);
+		if (status < 0)
+			return status;
+		else if (status == SUBMODULE_PATCH_WITHOUT_INDEX) {
+			/*
+			 * There is no way to apply subproject
+			 * patch without looking at the index.
+			 * NEEDSWORK: shouldn't this be flagged
+			 * as an error???
+			 */
+			free_fragment_list(patch->fragments);
+			patch->fragments = NULL;
+		} else if (status) {
 			return error(_("read of %s failed"), patch->old_name);
-	} else if (patch->old_name) {
-		if (S_ISGITLINK(patch->old_mode)) {
-			if (ce) {
-				read_file_or_gitlink(ce, &buf);
-			} else {
-				/*
-				 * There is no way to apply subproject
-				 * patch without looking at the index.
-				 * NEEDSWORK: shouldn't this be flagged
-				 * as an error???
-				 */
-				free_fragment_list(patch->fragments);
-				patch->fragments = NULL;
-			}
-		} else {
-			if (read_old_data(st, patch->old_name, &buf))
-				return error(_("read of %s failed"), patch->old_name);
 		}
 	}
 
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 09/19] apply: move check_to_create_blob() closer to its sole caller

[Junio C Hamano]

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 46 +++++++++++++++++++++++-----------------------
 1 file changed, 23 insertions(+), 23 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 35e9a9c..6431178 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3159,29 +3159,6 @@ static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *
 	return 0;
 }
 
-static int check_to_create_blob(const char *new_name, int ok_if_exists)
-{
-	struct stat nst;
-	if (!lstat(new_name, &nst)) {
-		if (S_ISDIR(nst.st_mode) || ok_if_exists)
-			return 0;
-		/*
-		 * A leading component of new_name might be a symlink
-		 * that is going to be removed with this patch, but
-		 * still pointing at somewhere that has the path.
-		 * In such a case, path "new_name" does not exist as
-		 * far as git is concerned.
-		 */
-		if (has_symlink_leading_path(new_name, strlen(new_name)))
-			return 0;
-
-		return error(_("%s: already exists in working directory"), new_name);
-	}
-	else if ((errno != ENOENT) && (errno != ENOTDIR))
-		return error("%s: %s", new_name, strerror(errno));
-	return 0;
-}
-
 static int verify_index_match(struct cache_entry *ce, struct stat *st)
 {
 	if (S_ISGITLINK(ce->ce_mode)) {
@@ -3266,6 +3243,29 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
 	return 0;
 }
 
+static int check_to_create_blob(const char *new_name, int ok_if_exists)
+{
+	struct stat nst;
+	if (!lstat(new_name, &nst)) {
+		if (S_ISDIR(nst.st_mode) || ok_if_exists)
+			return 0;
+		/*
+		 * A leading component of new_name might be a symlink
+		 * that is going to be removed with this patch, but
+		 * still pointing at somewhere that has the path.
+		 * In such a case, path "new_name" does not exist as
+		 * far as git is concerned.
+		 */
+		if (has_symlink_leading_path(new_name, strlen(new_name)))
+			return 0;
+
+		return error(_("%s: already exists in working directory"), new_name);
+	}
+	else if ((errno != ENOENT) && (errno != ENOTDIR))
+		return error("%s: %s", new_name, strerror(errno));
+	return 0;
+}
+
 /*
  * Check and apply the patch in-core; leave the result in patch->result
  * for the caller to write it out to the final destination.
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 10/19] apply: move "already exists" logic to check_to_create()

[Junio C Hamano]

The check_to_create_blob() function used to check only the case
where we are applying to the working tree.  Rename the function to
check_to_create() and make it also responsible for checking the case
where we apply to the index.  Also make its caller responsible for
issuing an error message.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 40 +++++++++++++++++++++++++++++-----------
 1 file changed, 29 insertions(+), 11 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 6431178..c4166b3 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3243,9 +3243,21 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
 	return 0;
 }
 
-static int check_to_create_blob(const char *new_name, int ok_if_exists)
+
+#define EXISTS_IN_INDEX 1
+#define EXISTS_IN_WORKTREE 2
+
+static int check_to_create(const char *new_name, int ok_if_exists)
 {
 	struct stat nst;
+
+	if (check_index &&
+	    cache_name_pos(new_name, strlen(new_name)) >= 0 &&
+	    !ok_if_exists)
+		return EXISTS_IN_INDEX;
+	if (cached)
+		return 0;
+
 	if (!lstat(new_name, &nst)) {
 		if (S_ISDIR(nst.st_mode) || ok_if_exists)
 			return 0;
@@ -3259,10 +3271,10 @@ static int check_to_create_blob(const char *new_name, int ok_if_exists)
 		if (has_symlink_leading_path(new_name, strlen(new_name)))
 			return 0;
 
-		return error(_("%s: already exists in working directory"), new_name);
-	}
-	else if ((errno != ENOENT) && (errno != ENOTDIR))
+		return EXISTS_IN_WORKTREE;
+	} else if ((errno != ENOENT) && (errno != ENOTDIR)) {
 		return error("%s: %s", new_name, strerror(errno));
+	}
 	return 0;
 }
 
@@ -3310,15 +3322,21 @@ static int check_patch(struct patch *patch)
 
 	if (new_name &&
 	    ((0 < patch->is_new) | (0 < patch->is_rename) | patch->is_copy)) {
-		if (check_index &&
-		    cache_name_pos(new_name, strlen(new_name)) >= 0 &&
-		    !ok_if_exists)
+		int err = check_to_create(new_name, ok_if_exists);
+
+		switch (err) {
+		case 0:
+			break; /* happy */
+		case EXISTS_IN_INDEX:
 			return error(_("%s: already exists in index"), new_name);
-		if (!cached) {
-			int err = check_to_create_blob(new_name, ok_if_exists);
-			if (err)
-				return err;
+			break;
+		case EXISTS_IN_WORKTREE:
+			return error(_("%s: already exists in working directory"),
+				     new_name);
+		default:
+			return err;
 		}
+
 		if (!patch->new_mode) {
 			if (0 < patch->is_new)
 				patch->new_mode = S_IFREG | 0644;
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 11/19] apply: accept -3/--3way command line option

[Junio C Hamano]

This is the beginning of teaching the three-way merge fallback logic "git
am -3" uses to the underlying "git apply".  It only implements the command
line parsing part, and does not do anything interesting yet, other than
making sure that "--reject" and "--3way" are not given together and
making "--3way" imply "--index".

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c         | 25 +++++++++++++++++++++++--
 t/t4117-apply-reject.sh |  8 ++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index c4166b3..509a297 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -46,6 +46,7 @@ static int apply_with_reject;
 static int apply_verbosely;
 static int allow_overlap;
 static int no_add;
+static int threeway;
 static const char *fake_ancestor;
 static int line_termination = '\n';
 static unsigned int p_context = UINT_MAX;
@@ -3139,6 +3140,12 @@ static int load_preimage(struct image *image,
 	return 0;
 }
 
+static int try_threeway(struct image *image, struct patch *patch,
+			struct stat *st, struct cache_entry *ce)
+{
+	return -1; /* for now */
+}
+
 static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *ce)
 {
 	struct image image;
@@ -3146,8 +3153,11 @@ static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *
 	if (load_preimage(&image, patch, st, ce) < 0)
 		return -1;
 
-	if (apply_fragments(&image, patch) < 0)
-		return -1; /* note with --reject this succeeds. */
+	if (apply_fragments(&image, patch) < 0) {
+		/* Note: with --reject, apply_fragments() returns 0 */
+		if (!threeway || try_threeway(&image, patch, st, ce) < 0)
+			return -1;
+	}
 	patch->result = image.buf;
 	patch->resultsize = image.len;
 	add_to_fn_table(patch);
@@ -4073,6 +4083,8 @@ int cmd_apply(int argc, const char **argv, const char *prefix_)
 			"apply a patch without touching the working tree"),
 		OPT_BOOLEAN(0, "apply", &force_apply,
 			"also apply the patch (use with --stat/--summary/--check)"),
+		OPT_BOOL('3', "3way", &threeway,
+			 "attempt three-way merge if a patch does not apply"),
 		OPT_FILENAME(0, "build-fake-ancestor", &fake_ancestor,
 			"build a temporary index based on embedded index information"),
 		{ OPTION_CALLBACK, 'z', NULL, NULL, NULL,
@@ -4121,6 +4133,15 @@ int cmd_apply(int argc, const char **argv, const char *prefix_)
 	argc = parse_options(argc, argv, prefix, builtin_apply_options,
 			apply_usage, 0);
 
+	if (apply_with_reject && threeway)
+		die("--reject and --3way cannot be used together.");
+	if (cached && threeway)
+		die("--cached and --3way cannot be used together.");
+	if (threeway) {
+		if (is_not_gitdir)
+			die(_("--3way outside a repository"));
+		check_index = 1;
+	}
 	if (apply_with_reject)
 		apply = apply_verbosely = 1;
 	if (!force_apply && (diffstat || numstat || summary || check || fake_ancestor))
diff --git a/t/t4117-apply-reject.sh b/t/t4117-apply-reject.sh
index e9ccd16..8e15ecb 100755
--- a/t/t4117-apply-reject.sh
+++ b/t/t4117-apply-reject.sh
@@ -46,6 +46,14 @@ test_expect_success setup '
 	cat file1 >saved.file1
 '
 
+test_expect_success 'apply --reject is incompatible with --3way' '
+	test_when_finished "cat saved.file1 >file1" &&
+	git diff >patch.0 &&
+	git checkout file1 &&
+	test_must_fail git apply --reject --3way patch.0 &&
+	git diff --exit-code
+'
+
 test_expect_success 'apply without --reject should fail' '
 
 	if git apply patch.1
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 12/19] apply: fall back on three-way merge

[Junio C Hamano]

Grab the preimage blob the patch claims to be based on out of the object
store, apply the patch, and then call three-way-merge function.  This step
still does not plug the actual three-way merge logic yet, but we are
getting there.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 46 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 509a297..6936588 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3140,10 +3140,54 @@ static int load_preimage(struct image *image,
 	return 0;
 }
 
+static int three_way_merge(struct image *image,
+			   char *path,
+			   unsigned char *base,
+			   unsigned char *ours,
+			   unsigned char *theirs)
+{
+	return -1; /* for now */
+}
+
 static int try_threeway(struct image *image, struct patch *patch,
 			struct stat *st, struct cache_entry *ce)
 {
-	return -1; /* for now */
+	unsigned char pre_sha1[20], post_sha1[20], our_sha1[20];
+	struct strbuf buf = STRBUF_INIT;
+	size_t len;
+	char *img;
+	struct image tmp_image;
+
+	/* No point falling back to 3-way merge in these cases */
+	if (patch->is_new || patch->is_delete ||
+	    S_ISGITLINK(patch->old_mode) || S_ISGITLINK(patch->new_mode))
+		return -1;
+
+	/* Preimage the patch was prepared for */
+	if (get_sha1(patch->old_sha1_prefix, pre_sha1) ||
+	    read_blob_object(&buf, pre_sha1, patch->old_mode))
+		return error("repository lacks the necessary blob to fall back on 3-way merge.");
+	img = strbuf_detach(&buf, &len);
+	prepare_image(&tmp_image, img, len, 1);
+	/* Apply the patch to get the post image */
+	if (apply_fragments(&tmp_image, patch) < 0) {
+		clear_image(&tmp_image);
+		return -1;
+	}
+	/* post_sha1[] is theirs */
+	write_sha1_file(tmp_image.buf, tmp_image.len, blob_type, post_sha1);
+	clear_image(&tmp_image);
+
+	/* our_sha1[] is ours */
+	if (load_preimage(&tmp_image, patch, st, ce))
+		return error("cannot read the current contents of '%s'",
+			     patch->old_name);
+	write_sha1_file(tmp_image.buf, tmp_image.len, blob_type, our_sha1);
+	clear_image(&tmp_image);
+
+	/* in-core three-way merge between post and our using pre as base */
+	return three_way_merge(image,
+			       patch->new_name, pre_sha1, our_sha1, post_sha1);
 }
 
 static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *ce)
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 13/19] apply: plug the three-way merge logic in

[Junio C Hamano]

When a patch does not apply to what we have, but we know the preimage the
patch was made against, we apply the patch to the preimage to compute what
the patch author wanted the result to look like, and attempt a three-way
merge between the result and our version, using the intended preimage as
the base version.

When we are applying the patch using the index, we would additionally need
to add the object names of these three blobs involved in the merge, which
is not yet done in this step, but we add a field to "struct patch" so that
later write-out step can use it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 53 insertions(+), 6 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 6936588..5ef8652 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -16,6 +16,8 @@
 #include "dir.h"
 #include "diff.h"
 #include "parse-options.h"
+#include "xdiff-interface.h"
+#include "ll-merge.h"
 
 /*
  *  --check turns on checking that the working tree matches the
@@ -194,12 +196,16 @@ struct patch {
 	unsigned int is_copy:1;
 	unsigned int is_rename:1;
 	unsigned int recount:1;
+	unsigned int conflicted_threeway:1;
 	struct fragment *fragments;
 	char *result;
 	size_t resultsize;
 	char old_sha1_prefix[41];
 	char new_sha1_prefix[41];
 	struct patch *next;
+
+	/* three-way fallback result */
+	unsigned char threeway_stage[3][20];
 };
 
 static void free_fragment_list(struct fragment *list)
@@ -3142,11 +3148,33 @@ static int load_preimage(struct image *image,
 
 static int three_way_merge(struct image *image,
 			   char *path,
-			   unsigned char *base,
-			   unsigned char *ours,
-			   unsigned char *theirs)
+			   const unsigned char *base,
+			   const unsigned char *ours,
+			   const unsigned char *theirs)
 {
-	return -1; /* for now */
+	mmfile_t base_file, our_file, their_file;
+	mmbuffer_t result = { NULL };
+	int status;
+
+	read_mmblob(&base_file, base);
+	read_mmblob(&our_file, ours);
+	read_mmblob(&their_file, theirs);
+	status = ll_merge(&result, path,
+			  &base_file, "base",
+			  &our_file, "ours",
+			  &their_file, "theirs", NULL);
+	free(base_file.ptr);
+	free(our_file.ptr);
+	free(their_file.ptr);
+	if (status < 0 || !result.ptr) {
+		free(result.ptr);
+		return -1;
+	}
+	clear_image(image);
+	image->buf = result.ptr;
+	image->len = result.size;
+
+	return status;
 }
 
 static int try_threeway(struct image *image, struct patch *patch,
@@ -3155,6 +3183,7 @@ static int try_threeway(struct image *image, struct patch *patch,
 	unsigned char pre_sha1[20], post_sha1[20], our_sha1[20];
 	struct strbuf buf = STRBUF_INIT;
 	size_t len;
+	int status;
 	char *img;
 	struct image tmp_image;
 
@@ -3167,6 +3196,9 @@ static int try_threeway(struct image *image, struct patch *patch,
 	if (get_sha1(patch->old_sha1_prefix, pre_sha1) ||
 	    read_blob_object(&buf, pre_sha1, patch->old_mode))
 		return error("repository lacks the necessary blob to fall back on 3-way merge.");
+
+	fprintf(stderr, "Falling back to three-way merge...\n");
+
 	img = strbuf_detach(&buf, &len);
 	prepare_image(&tmp_image, img, len, 1);
 	/* Apply the patch to get the post image */
@@ -3186,8 +3218,23 @@ static int try_threeway(struct image *image, struct patch *patch,
 	clear_image(&tmp_image);
 
 	/* in-core three-way merge between post and our using pre as base */
-	return three_way_merge(image,
-			       patch->new_name, pre_sha1, our_sha1, post_sha1);
+	status = three_way_merge(image, patch->new_name,
+				 pre_sha1, our_sha1, post_sha1);
+	if (status < 0) {
+		fprintf(stderr, "Failed to fall back on three-way merge...\n");
+		return status;
+	}
+
+	if (status) {
+		patch->conflicted_threeway = 1;
+		hashcpy(patch->threeway_stage[0], pre_sha1);
+		hashcpy(patch->threeway_stage[1], our_sha1);
+		hashcpy(patch->threeway_stage[2], post_sha1);
+		fprintf(stderr, "Applied patch to '%s' with conflicts.\n", patch->new_name);
+	} else {
+		fprintf(stderr, "Applied patch to '%s' cleanly.\n", patch->new_name);
+	}
+	return 0;
 }
 
 static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *ce)
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 14/19] apply: move verify_index_match() higher

[Junio C Hamano]

We will be adding another caller of this function in a later patch.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 5ef8652..8bc4218 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3074,6 +3074,16 @@ static struct patch *previous_patch(struct patch *patch, int *gone)
 	return previous;
 }
 
+static int verify_index_match(struct cache_entry *ce, struct stat *st)
+{
+	if (S_ISGITLINK(ce->ce_mode)) {
+		if (!S_ISDIR(st->st_mode))
+			return -1;
+		return 0;
+	}
+	return ce_match_stat(ce, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
+}
+
 #define SUBMODULE_PATCH_WITHOUT_INDEX 1
 
 static int load_patch_target(struct strbuf *buf,
@@ -3260,16 +3270,6 @@ static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *
 	return 0;
 }
 
-static int verify_index_match(struct cache_entry *ce, struct stat *st)
-{
-	if (S_ISGITLINK(ce->ce_mode)) {
-		if (!S_ISDIR(st->st_mode))
-			return -1;
-		return 0;
-	}
-	return ce_match_stat(ce, st, CE_MATCH_IGNORE_VALID|CE_MATCH_IGNORE_SKIP_WORKTREE);
-}
-
 /*
  * If "patch" that we are looking at modifies or deletes what we have,
  * we would want it not to lose any local modification we have, either
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 15/19] apply: --3way with add/add conflict

[Junio C Hamano]

When a patch wants to create a path, but we already have it in our
current state, pretend as if the patch and we independently added
the same path and cause add/add conflict, so that the user can
resolve it just like "git merge" in the same situation.

For that purpose, implement load_current() in terms of the
load_patch_target() helper introduced earlier to read the current
contents from the path given by patch->new_name (patch->old_name is
NULL for a creation patch).

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 62 insertions(+), 8 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index 8bc4218..c3b9f76 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -197,6 +197,7 @@ struct patch {
 	unsigned int is_rename:1;
 	unsigned int recount:1;
 	unsigned int conflicted_threeway:1;
+	unsigned int direct_to_threeway:1;
 	struct fragment *fragments;
 	char *result;
 	size_t resultsize;
@@ -3187,6 +3188,48 @@ static int three_way_merge(struct image *image,
 	return status;
 }
 
+/*
+ * When directly falling back to add/add three-way merge, we read from
+ * the current contents of the new_name.  In no cases other than that
+ * this function will be called.
+ */
+static int load_current(struct image *image, struct patch *patch)
+{
+	struct strbuf buf = STRBUF_INIT;
+	int status, pos;
+	size_t len;
+	char *img;
+	struct stat st;
+	struct cache_entry *ce;
+	char *name = patch->new_name;
+	unsigned mode = patch->new_mode;
+
+	if (!patch->is_new)
+		die("BUG: patch to %s is not a creation", patch->old_name);
+
+	pos = cache_name_pos(name, strlen(name));
+	if (pos < 0)
+		return error(_("%s: does not exist in index"), name);
+	ce = active_cache[pos];
+	if (lstat(name, &st)) {
+		if (errno != ENOENT)
+			return error(_("%s: %s"), name, strerror(errno));
+		if (checkout_target(ce, &st))
+			return -1;
+	}
+	if (verify_index_match(ce, &st))
+		return error(_("%s: does not match index"), name);
+
+	status = load_patch_target(&buf, ce, &st, name, mode);
+	if (status < 0)
+		return status;
+	else if (status)
+		return -1;
+	img = strbuf_detach(&buf, &len);
+	prepare_image(image, img, len, !patch->is_binary);
+	return 0;
+}
+
 static int try_threeway(struct image *image, struct patch *patch,
 			struct stat *st, struct cache_entry *ce)
 {
@@ -3198,13 +3241,15 @@ static int try_threeway(struct image *image, struct patch *patch,
 	struct image tmp_image;
 
 	/* No point falling back to 3-way merge in these cases */
-	if (patch->is_new || patch->is_delete ||
+	if (patch->is_delete ||
 	    S_ISGITLINK(patch->old_mode) || S_ISGITLINK(patch->new_mode))
 		return -1;
 
 	/* Preimage the patch was prepared for */
-	if (get_sha1(patch->old_sha1_prefix, pre_sha1) ||
-	    read_blob_object(&buf, pre_sha1, patch->old_mode))
+	if (patch->is_new)
+		write_sha1_file("", 0, blob_type, pre_sha1);
+	else if (get_sha1(patch->old_sha1_prefix, pre_sha1) ||
+		 read_blob_object(&buf, pre_sha1, patch->old_mode))
 		return error("repository lacks the necessary blob to fall back on 3-way merge.");
 
 	fprintf(stderr, "Falling back to three-way merge...\n");
@@ -3221,9 +3266,15 @@ static int try_threeway(struct image *image, struct patch *patch,
 	clear_image(&tmp_image);
 
 	/* our_sha1[] is ours */
-	if (load_preimage(&tmp_image, patch, st, ce))
-		return error("cannot read the current contents of '%s'",
-			     patch->old_name);
+	if (patch->is_new) {
+		if (load_current(&tmp_image, patch))
+			return error("cannot read the current contents of '%s'",
+				     patch->new_name);
+	} else {
+		if (load_preimage(&tmp_image, patch, st, ce))
+			return error("cannot read the current contents of '%s'",
+				     patch->old_name);
+	}
 	write_sha1_file(tmp_image.buf, tmp_image.len, blob_type, our_sha1);
 	clear_image(&tmp_image);
 
@@ -3254,7 +3305,8 @@ static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *
 	if (load_preimage(&image, patch, st, ce) < 0)
 		return -1;
 
-	if (apply_fragments(&image, patch) < 0) {
+	if (patch->direct_to_threeway ||
+	    apply_fragments(&image, patch) < 0) {
 		/* Note: with --reject, apply_fragments() returns 0 */
 		if (!threeway || try_threeway(&image, patch, st, ce) < 0)
 			return -1;
@@ -3425,7 +3477,9 @@ static int check_patch(struct patch *patch)
 	    ((0 < patch->is_new) | (0 < patch->is_rename) | patch->is_copy)) {
 		int err = check_to_create(new_name, ok_if_exists);
 
-		switch (err) {
+		if (err && threeway) {
+			patch->direct_to_threeway = 1;
+		} else switch (err) {
 		case 0:
 			break; /* happy */
 		case EXISTS_IN_INDEX:
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 16/19] apply: register conflicted stages to the index

[Junio C Hamano]

Now we have all the necessary logic to fall back on three-way merge when
the patch does not cleanly apply, insert the conflicted entries to the
index as appropriate.  This obviously triggers only when the "--index"
option is used.

When we fall back to three-way merge and some of the merges fail, just
like the case where the "--reject" option was specified and we had to
write some "*.rej" files out for unapplicable patches, exit the command
with non-zero status without showing the diffstat and summary.  Otherwise
they would make the list of problematic paths scroll off the display.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c           | 65 +++++++++++++++++++++++++++++++++++----
 t/t4108-apply-threeway.sh | 78 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 137 insertions(+), 6 deletions(-)
 create mode 100755 t/t4108-apply-threeway.sh

diff --git a/builtin/apply.c b/builtin/apply.c
index c3b9f76..8afba92 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3288,7 +3288,10 @@ static int try_threeway(struct image *image, struct patch *patch,
 
 	if (status) {
 		patch->conflicted_threeway = 1;
-		hashcpy(patch->threeway_stage[0], pre_sha1);
+		if (patch->is_new)
+			hashclr(patch->threeway_stage[0]);
+		else
+			hashcpy(patch->threeway_stage[0], pre_sha1);
 		hashcpy(patch->threeway_stage[1], our_sha1);
 		hashcpy(patch->threeway_stage[2], post_sha1);
 		fprintf(stderr, "Applied patch to '%s' with conflicts.\n", patch->new_name);
@@ -3846,6 +3849,32 @@ static void create_one_file(char *path, unsigned mode, const char *buf, unsigned
 	die_errno(_("unable to write file '%s' mode %o"), path, mode);
 }
 
+static void add_conflicted_stages_file(struct patch *patch)
+{
+	int stage, namelen;
+	unsigned ce_size, mode;
+	struct cache_entry *ce;
+
+	if (!update_index)
+		return;
+	namelen = strlen(patch->new_name);
+	ce_size = cache_entry_size(namelen);
+	mode = patch->new_mode ? patch->new_mode : (S_IFREG | 0644);
+
+	remove_file_from_cache(patch->new_name);
+	for (stage = 1; stage < 4; stage++) {
+		if (is_null_sha1(patch->threeway_stage[stage - 1]))
+			continue;
+		ce = xcalloc(1, ce_size);
+		memcpy(ce->name, patch->new_name, namelen);
+		ce->ce_mode = create_ce_mode(mode);
+		ce->ce_flags = create_ce_flags(namelen, stage);
+		hashcpy(ce->sha1, patch->threeway_stage[stage - 1]);
+		if (add_cache_entry(ce, ADD_CACHE_OK_TO_ADD) < 0)
+			die(_("unable to add cache entry for %s"), patch->new_name);
+	}
+}
+
 static void create_file(struct patch *patch)
 {
 	char *path = patch->new_name;
@@ -3856,7 +3885,11 @@ static void create_file(struct patch *patch)
 	if (!mode)
 		mode = S_IFREG | 0644;
 	create_one_file(path, mode, buf, size);
-	add_index_file(path, mode, buf, size);
+
+	if (patch->conflicted_threeway)
+		add_conflicted_stages_file(patch);
+	else
+		add_index_file(path, mode, buf, size);
 }
 
 /* phase zero is to remove, phase one is to create */
@@ -3958,6 +3991,7 @@ static int write_out_results(struct patch *list)
 	int phase;
 	int errs = 0;
 	struct patch *l;
+	struct string_list cpath = STRING_LIST_INIT_DUP;
 
 	for (phase = 0; phase < 2; phase++) {
 		l = list;
@@ -3966,12 +4000,28 @@ static int write_out_results(struct patch *list)
 				errs = 1;
 			else {
 				write_out_one_result(l, phase);
-				if (phase == 1 && write_out_one_reject(l))
-					errs = 1;
+				if (phase == 1) {
+					if (write_out_one_reject(l))
+						errs = 1;
+					if (l->conflicted_threeway) {
+						string_list_append(&cpath, l->new_name);
+						errs = 1;
+					}
+				}
 			}
 			l = l->next;
 		}
 	}
+
+	if (cpath.nr) {
+		struct string_list_item *item;
+
+		sort_string_list(&cpath);
+		for_each_string_list_item(item, &cpath)
+			fprintf(stderr, "U %s\n", item->string);
+		string_list_clear(&cpath, 0);
+	}
+
 	return errs;
 }
 
@@ -4094,8 +4144,11 @@ static int apply_patch(int fd, const char *filename, int options)
 	    !apply_with_reject)
 		exit(1);
 
-	if (apply && write_out_results(list))
-		exit(1);
+	if (apply && write_out_results(list)) {
+		if (apply_with_reject)
+			exit(1);
+		return 1;
+	}
 
 	if (fake_ancestor)
 		build_fake_ancestor(list, fake_ancestor);
diff --git a/t/t4108-apply-threeway.sh b/t/t4108-apply-threeway.sh
new file mode 100755
index 0000000..475dfb5
--- /dev/null
+++ b/t/t4108-apply-threeway.sh
@@ -0,0 +1,78 @@
+#!/bin/sh
+
+test_description='git apply --3way'
+
+. ./test-lib.sh
+
+create_file () {
+	for i
+	do
+		echo "$i"
+	done
+}
+
+sanitize_conflicted_diff () {
+	sed -e '
+		/^index /d
+		s/^\(+[<>][<>][<>][<>]*\) .*/\1/
+	'
+}
+
+test_expect_success setup '
+	test_tick &&
+	create_file >one 1 2 3 4 5 6 7 &&
+	cat one >two &&
+	git add one two &&
+	git commit -m initial &&
+
+	git branch side &&
+
+	test_tick &&
+	create_file >one 1 two 3 4 5 six 7 &&
+	create_file >two 1 two 3 4 5 6 7 &&
+	git commit -a -m master &&
+
+	git checkout side &&
+	create_file >one 1 2 3 4 five 6 7 &&
+	create_file >two 1 2 3 4 five 6 7 &&
+	git commit -a -m side &&
+
+	git checkout master
+'
+
+test_expect_success 'apply without --3way' '
+	git diff side^ side >P.diff &&
+
+	# should fail to apply
+	git reset --hard &&
+	git checkout master^0 &&
+	test_must_fail git apply --index P.diff &&
+	# should leave things intact
+	git diff-files --exit-code &&
+	git diff-index --exit-code --cached HEAD
+'
+
+test_expect_success 'apply with --3way' '
+	# Merging side should be similar to applying this patch
+	git diff ...side >P.diff &&
+
+	# The corresponding conflicted merge
+	git reset --hard &&
+	git checkout master^0 &&
+	test_must_fail git merge --no-commit side &&
+	git ls-files -s >expect.ls &&
+	git diff HEAD | sanitize_conflicted_diff >expect.diff &&
+
+	# should fail to apply
+	git reset --hard &&
+	git checkout master^0 &&
+	test_must_fail git apply --index --3way P.diff &&
+	git ls-files -s >actual.ls &&
+	git diff HEAD | sanitize_conflicted_diff >actual.diff &&
+
+	# The result should resemble the corresponding merge
+	test_cmp expect.ls actual.ls &&
+	test_cmp expect.diff actual.diff
+'
+
+test_done
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 17/19] apply: allow rerere() upon --3way results

[Junio C Hamano]

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c           |  3 +++
 t/t4108-apply-threeway.sh | 25 +++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/builtin/apply.c b/builtin/apply.c
index 8afba92..d12f4f2 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -18,6 +18,7 @@
 #include "parse-options.h"
 #include "xdiff-interface.h"
 #include "ll-merge.h"
+#include "rerere.h"
 
 /*
  *  --check turns on checking that the working tree matches the
@@ -4020,6 +4021,8 @@ static int write_out_results(struct patch *list)
 		for_each_string_list_item(item, &cpath)
 			fprintf(stderr, "U %s\n", item->string);
 		string_list_clear(&cpath, 0);
+
+		rerere(0);
 	}
 
 	return errs;
diff --git a/t/t4108-apply-threeway.sh b/t/t4108-apply-threeway.sh
index 475dfb5..e6d4da6 100755
--- a/t/t4108-apply-threeway.sh
+++ b/t/t4108-apply-threeway.sh
@@ -75,4 +75,29 @@ test_expect_success 'apply with --3way' '
 	test_cmp expect.diff actual.diff
 '
 
+test_expect_success 'apply with --3way with rerere enabled' '
+	git config rerere.enabled true &&
+
+	# Merging side should be similar to applying this patch
+	git diff ...side >P.diff &&
+
+	# The corresponding conflicted merge
+	git reset --hard &&
+	git checkout master^0 &&
+	test_must_fail git merge --no-commit side &&
+
+	# Manually resolve and record the resolution
+	create_file 1 two 3 4 five six 7 >one &&
+	git rerere &&
+	cat one >expect &&
+
+	# should fail to apply
+	git reset --hard &&
+	git checkout master^0 &&
+	test_must_fail git apply --index --3way P.diff &&
+
+	# but rerere should have replayed the recorded resolution
+	test_cmp expect one
+'
+
 test_done
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 18/19] apply: document --3way option

[Junio C Hamano]

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-apply.txt | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-apply.txt b/Documentation/git-apply.txt
index afd2c9a..634b84e 100644
--- a/Documentation/git-apply.txt
+++ b/Documentation/git-apply.txt
@@ -9,7 +9,7 @@ git-apply - Apply a patch to files and/or to the index
 SYNOPSIS
 --------
 [verse]
-'git apply' [--stat] [--numstat] [--summary] [--check] [--index]
+'git apply' [--stat] [--numstat] [--summary] [--check] [--index] [--3way]
 	  [--apply] [--no-add] [--build-fake-ancestor=<file>] [-R | --reverse]
 	  [--allow-binary-replacement | --binary] [--reject] [-z]
 	  [-p<n>] [-C<n>] [--inaccurate-eof] [--recount] [--cached]
@@ -72,6 +72,15 @@ OPTIONS
 	cached data, apply the patch, and store the result in the index
 	without using the working tree. This implies `--index`.
 
+-3::
+--3way::
+	When the patch does not apply cleanly, fall back on 3-way merge if
+	the patch records the identity of blobs it is supposed to apply to,
+	and we have those blobs available locally, possibly leaving the
+	conflict markers in the files in the working tree for the user to
+	resolve.  This option implies the `--index` option, and is incompatible
+	with the `--reject` and the `--cached` options.
+
 --build-fake-ancestor=<file>::
 	Newer 'git diff' output has embedded 'index information'
 	for each blob to help identify the original version that
-- 
1.7.11.rc3.30.g3bdace2

[PATCH v3 19/19] apply --3way: tests

[Junio C Hamano]

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 t/t4108-apply-threeway.sh | 54 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/t/t4108-apply-threeway.sh b/t/t4108-apply-threeway.sh
index e6d4da6..fa5d4ef 100755
--- a/t/t4108-apply-threeway.sh
+++ b/t/t4108-apply-threeway.sh
@@ -100,4 +100,58 @@ test_expect_success 'apply with --3way with rerere enabled' '
 	test_cmp expect one
 '
 
+test_expect_success 'apply -3 with add/add conflict setup' '
+	git reset --hard &&
+
+	git checkout -b adder &&
+	create_file 1 2 3 4 5 6 7 >three &&
+	create_file 1 2 3 4 5 6 7 >four &&
+	git add three four &&
+	git commit -m "add three and four" &&
+
+	git checkout -b another adder^ &&
+	create_file 1 2 3 4 5 6 7 >three &&
+	create_file 1 2 3 four 5 6 7 >four &&
+	git add three four &&
+	git commit -m "add three and four" &&
+
+	# Merging another should be similar to applying this patch
+	git diff adder...another >P.diff &&
+
+	git checkout adder^0 &&
+	test_must_fail git merge --no-commit another &&
+	git ls-files -s >expect.ls &&
+	git diff HEAD | sanitize_conflicted_diff >expect.diff
+'
+
+test_expect_success 'apply -3 with add/add conflict' '
+	# should fail to apply ...
+	git reset --hard &&
+	git checkout adder^0 &&
+	test_must_fail git apply --index --3way P.diff &&
+	# ... and leave conflicts in the index and in the working tree
+	git ls-files -s >actual.ls &&
+	git diff HEAD | sanitize_conflicted_diff >actual.diff &&
+
+	# The result should resemble the corresponding merge
+	test_cmp expect.ls actual.ls &&
+	test_cmp expect.diff actual.diff
+'
+
+test_expect_success 'apply -3 with add/add conflict (dirty working tree)' '
+	# should fail to apply ...
+	git reset --hard &&
+	git checkout adder^0 &&
+	echo >>four &&
+	cat four >four.save &&
+	cat three >three.save &&
+	git ls-files -s >expect.ls &&
+	test_must_fail git apply --index --3way P.diff &&
+	# ... and should not touch anything
+	git ls-files -s >actual.ls &&
+	test_cmp expect.ls actual.ls &&
+	test_cmp four.save four &&
+	test_cmp three.save three
+'
+
 test_done
-- 
1.7.11.rc3.30.g3bdace2