Store peeled refs in packed-refs (take 2).

This fixes the previous implementation which failed to optimize
repositories with tons of lightweight tags.  The updated
packed-refs format begins with "# packed-refs with:" line that
lists the kind of extended data the file records.  Currently,
there is only one such extension defined, "peeled".  This stores
the "peeled tag" on a line that immediately follows a line for a
tag object itself in the format "^<sha-1>".

The header line itself and any extended data are ignored by
older implementation, so packed-refs file generated with this
version can still be used by older git.  packed-refs made by
older git can of course be used with this version.

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

1 files changed, 6 insertions, 2 deletions

diff --git a/builtin-pack-refs.c b/builtin-pack-refs.c
index ee5a5565af..8dc5b9efff 100644
--- a/builtin-pack-refs.c
+++ b/builtin-pack-refs.c
@@ -46,8 +46,8 @@ static int handle_one_ref(const char *path, const unsigned char *sha1,
 		if (o->type == OBJ_TAG) {
 			o = deref_tag(o, path, 0);
 			if (o)
-				fprintf(cb->refs_file, "%s  %s^{}\n",
-					sha1_to_hex(o->sha1), path);
+				fprintf(cb->refs_file, "^%s\n",
+					sha1_to_hex(o->sha1));
 		}
 	}
 
@@ -111,6 +111,10 @@ int cmd_pack_refs(int argc, const char **argv, const char *prefix)
 	if (!cbdata.refs_file)
 		die("unable to create ref-pack file structure (%s)",
 		    strerror(errno));
+
+	/* perhaps other traits later as well */
+	fprintf(cbdata.refs_file, "# pack-refs with: peeled \n");
+
 	for_each_ref(handle_one_ref, &cbdata);
 	fflush(cbdata.refs_file);
 	fsync(fd);