object: add repository argument to parse_object_buffer

Add a repository argument to allow the callers of parse_object_buffer
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>

builtin/unpack-objects.c

@@ -265,7 +265,8 @@ static void write_object(unsigned nr, enum object_type type,
 		int eaten;
 		hash_object_file(buf, size, type_name(type), &obj_list[nr].oid);
 		added_object(nr, type, buf, size);
-		obj = parse_object_buffer(&obj_list[nr].oid, type, size, buf,
+		obj = parse_object_buffer(the_repository, &obj_list[nr].oid,
+					  type, size, buf,
 					  &eaten);
 		if (!obj)
 			die("invalid %s", type_name(type));