remote.sync: keep a changed object even with no entry at its path

Deleting a changed object when no entry holds the path also deletes a
copy a directory rename has written but not yet made visible, while a
delete of that path waits in the sync; the rename then removes the old
key and the content is gone. Keep any object whose ETag changed since
the delete, as before. An upload that finishes after the delete leaks
its object instead, which is the cheaper failure.

weed/command/filer_remote_sync_dir_test.go

@@ -1053,17 +1053,17 @@ func TestDeleteEventAbsentRemoteObjectIsSuccess(t *testing.T) {
 		}
 	})
 
-	t.Run("a changed object with no entry at the path still goes", func(t *testing.T) {
-		// an upload that finished after the delete leaves a newer object that
-		// no entry describes; keeping it would leave it on the remote forever
+	t.Run("a changed object with no entry at the path yet is kept", func(t *testing.T) {
+		// a directory rename copies a child onto the key before its new entry
+		// becomes visible; the copy may be the content's only remaining home
 		deleted := proto.Clone(resp).(*filer_pb.SubscribeMetadataResponse)
 		deleted.EventNotification.OldEntry.RemoteEntry = &filer_pb.RemoteEntry{RemoteETag: `"orig"`, RemoteSize: 10}
-		remote := &recordingRemote{objects: map[string][]byte{"/b/vol/state.db.tmp": []byte("late")}, statETag: `"late"`}
+		remote := &recordingRemote{objects: map[string][]byte{"/b/vol/state.db.tmp": []byte("copied")}, statETag: `"copy"`}
 		if err := processDeleteEvent(&stubFilerClient{}, remote, mountedDir, mountLoc, deleted); err != nil {
 			t.Fatalf("err = %v", err)
 		}
-		if len(remote.deletes) != 1 {
-			t.Errorf("deletes = %+v, want one", remote.deletes)
+		if len(remote.deletes) != 0 {
+			t.Errorf("deletes = %+v, want none", remote.deletes)
 		}
 	})