object: add repository argument to parse_object

Add a repository argument to allow the callers of parse_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.

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

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>

object.h

@@ -120,7 +120,8 @@ void *object_as_type(struct object *obj, enum object_type type, int quiet);
  *
  * Returns NULL if the object is missing or corrupt.
  */
-struct object *parse_object(const struct object_id *oid);
+#define parse_object(r, oid) parse_object_##r(oid)
+struct object *parse_object_the_repository(const struct object_id *oid);
 
 /*
  * Like parse_object, but will die() instead of returning NULL. If the