return ret;
 }
 
-int checkout_fast_forward(const unsigned char *head,
-                         const unsigned char *remote,
+int checkout_fast_forward(const struct object_id *head,
+                         const struct object_id *remote,
                          int overwrite_ignore)
 {
        struct tree *trees[MAX_UNPACK_TREES];
 
        refresh_cache(REFRESH_QUIET);
 
-       if (hold_locked_index(lock_file, 0) < 0)
+       if (hold_locked_index(lock_file, LOCK_REPORT_ON_ERROR) < 0)
                return -1;
 
        memset(&trees, 0, sizeof(trees));