object: add repository argument to lookup_object

Add a repository argument to allow callers of lookup_object 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>

http-push.c

@@ -722,7 +722,7 @@ static void one_remote_object(const struct object_id *oid)
 {
 	struct object *obj;
 
-	obj = lookup_object(oid->hash);
+	obj = lookup_object(the_repository, oid->hash);
 	if (!obj)
 		obj = parse_object(the_repository, oid);