replace-object: add repository argument to do_lookup_replace_object

Add a repository argument to allow the do_lookup_replace_object caller
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: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

replace_object.c

@@ -55,7 +55,7 @@ static void prepare_replace_object_the_repository(void)
  * permanently-allocated value.  This function always respects replace
  * references, regardless of the value of check_replace_refs.
  */
-const struct object_id *do_lookup_replace_object(const struct object_id *oid)
+const struct object_id *do_lookup_replace_object_the_repository(const struct object_id *oid)
 {
 	int depth = MAXREPLACEDEPTH;
 	const struct object_id *cur = oid;