replace-object: use hash algorithm from passed-in repository

In `register_replace_ref()`, we pass in a repository but then use
`get_oid_hex()` to parse passed-in object IDs, which implicitly uses
`the_repository`. Fix this by using the hash algorithm from the
passed-in repository instead.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: pks-t

replace-object.c

@@ -20,7 +20,7 @@ static int register_replace_ref(const char *refname,
 	const char *hash = slash ? slash + 1 : refname;
 	struct replace_object *repl_obj = xmalloc(sizeof(*repl_obj));
 
-	if (get_oid_hex(hash, &repl_obj->original.oid)) {
+	if (get_oid_hex_algop(hash, &repl_obj->original.oid, r->hash_algo)) {
 		free(repl_obj);
 		warning(_("bad replace ref name: %s"), refname);
 		return 0;