[PATCH 6/8] apply: fall back on three-way merge

From

Junio C Hamano <gitster@pobox.com>

Date

May 10, 2012, 06:02 UTC

Message-ID

<1336629745-22436-7-git-send-email-gitster@pobox.com>

In-Reply-To

<1336629745-22436-1-git-send-email-gitster@pobox.com>

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 builtin/apply.c | 46 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 44 insertions(+), 2 deletions(-)

diff --git a/builtin/apply.c b/builtin/apply.c
index b1dd23c..798a634 100644
--- a/builtin/apply.c
+++ b/builtin/apply.c
@@ -3073,11 +3073,53 @@ static int load_preimage(struct image *image,
 	return 0;
 }
 
-static int try_threeway_fallback(struct image *image, struct patch *patch)
+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_fallback(struct image *image, struct patch *patch,
+				 struct stat *st, struct cache_entry *ce)
+{
+	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_binary || 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 necessary blobs 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;
+	}
+	hash_sha1_file(tmp_image.buf, tmp_image.len, blob_type, post_sha1);
+	clear_image(&tmp_image);
+
+	/* pre_sha1[] is common, post_sha1[] is theirs */
+	load_preimage(&tmp_image, patch, st, ce);
+	hash_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)
 {
 	struct image image;
@@ -3087,7 +3129,7 @@ static int apply_data(struct patch *patch, struct stat *st, struct cache_entry *
 
 	if (apply_fragments(&image, patch) < 0) {
 		/* Note: with --reject, the above call succeeds. */
-		if (!threeway || try_threeway_fallback(&image, patch) < 0)
+		if (!threeway || try_threeway_fallback(&image, patch, st, ce) < 0)
 			return -1;
 	}
 	patch->result = image.buf;

-- 
1.7.10.1.562.gfc79b1c