object: add repository argument to create_object

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

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

commit.c

@@ -50,7 +50,8 @@ struct commit *lookup_commit(const struct object_id *oid)
 {
 	struct object *obj = lookup_object(oid->hash);
 	if (!obj)
-		return create_object(oid->hash, alloc_commit_node());
+		return create_object(the_repository, oid->hash,
+				     alloc_commit_node());
 	return object_as_type(obj, OBJ_COMMIT, 0);
 }