commit: add repository argument to lookup_commit_reference_gently

Add a repository argument to allow callers of
lookup_commit_reference_gently to be more specific about which
repository to handle. This is a small mechanical change; it doesn't
change the implementation to handle repositories other than
the_repository yet.

As with the previous commits, use a macro to catch callers passing a
repository other than the_repository at compile time.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

commit.c

@@ -24,8 +24,8 @@ int save_commit_buffer = 1;
 
 const char *commit_type = "commit";
 
-struct commit *lookup_commit_reference_gently(const struct object_id *oid,
-					      int quiet)
+struct commit *lookup_commit_reference_gently_the_repository(
+		const struct object_id *oid, int quiet)
 {
 	struct object *obj = deref_tag(parse_object(the_repository, oid),
 				       NULL, 0);
@@ -37,7 +37,7 @@ struct commit *lookup_commit_reference_gently(const struct object_id *oid,
 
 struct commit *lookup_commit_reference(const struct object_id *oid)
 {
-	return lookup_commit_reference_gently(oid, 0);
+	return lookup_commit_reference_gently(the_repository, oid, 0);
 }
 
 struct commit *lookup_commit_or_die(const struct object_id *oid, const char *ref_name)