Convert check_connected to use struct object_id

Convert check_connected and the callbacks it takes to use struct
object_id.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 859be91..e705237 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -727,7 +727,7 @@ static int update_local_ref(struct ref *ref,
 	}
 }
 
-static int iterate_ref_map(void *cb_data, unsigned char sha1[20])
+static int iterate_ref_map(void *cb_data, struct object_id *oid)
 {
 	struct ref **rm = cb_data;
 	struct ref *ref = *rm;
@@ -737,7 +737,7 @@ static int iterate_ref_map(void *cb_data, unsigned char sha1[20])
 	if (!ref)
 		return -1; /* end of the list */
 	*rm = ref->next;
-	hashcpy(sha1, ref->old_oid.hash);
+	oidcpy(oid, &ref->old_oid);
 	return 0;
 }