Teach parse_commit_buffer about grafting.

Introduce a new file $GIT_DIR/info/grafts (or $GIT_GRAFT_FILE)
which is a list of "fake commit parent records".  Each line of
this file is a commit ID, followed by parent commit IDs, all
40-byte hex SHA1 separated by a single SP in between.  The
records override the parent information we would normally read
from the commit objects, allowing both adding "fake" parents
(i.e. grafting), and pretending as if a commit is not a child of
some of its real parents (i.e. cauterizing).

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 12 insertions, 1 deletions

diff --git a/sha1_file.c b/sha1_file.c
index eba5a36f24..8d3a65f5f8 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -61,7 +61,8 @@ static int get_sha1_file(const char *path, unsigned char *result)
 	return get_sha1_hex(buffer, result);
 }
 
-static char *git_dir, *git_object_dir, *git_index_file, *git_refs_dir;
+static char *git_dir, *git_object_dir, *git_index_file, *git_refs_dir,
+	*git_graft_file;
 static void setup_git_env(void)
 {
 	git_dir = gitenv(GIT_DIR_ENVIRONMENT);
@@ -79,6 +80,9 @@ static void setup_git_env(void)
 		git_index_file = xmalloc(strlen(git_dir) + 7);
 		sprintf(git_index_file, "%s/index", git_dir);
 	}
+	git_graft_file = gitenv(GRAFT_ENVIRONMENT);
+	if (!git_graft_file)
+		git_graft_file = strdup(git_path("info/grafts"));
 }
 
 char *get_object_directory(void)
@@ -102,6 +106,13 @@ char *get_index_file(void)
 	return git_index_file;
 }
 
+char *get_graft_file(void)
+{
+	if (!git_graft_file)
+		setup_git_env();
+	return git_graft_file;
+}
+
 int safe_create_leading_directories(char *path)
 {
 	char *pos = path;