builtin-fast-export.c: turn error into warning

fast-import doesn't have a syntax to support tree-objects (and some other
object-types), so fast-export shouldn't handle them. However, aborting the
operation is a bit drastic. This patch turns the error into a warning instead.
Signed-off-by: NErik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-fast-export.c

@@ -378,8 +378,10 @@ static void get_tags_and_duplicates(struct object_array *pending,
 			}
 			break;
 		default:
-			die ("Unexpected object of type %s",
-			     typename(e->item->type));
+			warning("%s: Unexpected object of type %s, skipping.",
+				e->name,
+				typename(e->item->type));
+			continue;
 		}
 		if (commit->util)
 			/* more than one name for the same object */