anchor.diff:          "ref: ${localHeadRef.name}\n", "Text").then((_) {
         return FileOps.createFileWithContent(gitDir, localHeadRef.name,
             localHeadRef.sha, "Text").then((_) {
  -        return fetcher.fetchRef([localHeadRef.sha], null, null, _options.depth,
  -            null, nopFunction, nopFunction).then((PackParseResult result) {
  +        return callMethod(fetcher.fetchRef, [[localHeadRef.sha], null, null,
  +            _options.depth, null, nopFunction, nopFunction, cancel]).then(
  +            (PackParseResult result) {
             Uint8List packData = result.data;
             List<int> packSha = packData.sublist(packData.length - 20);
             Uint8List packIdxData = PackIndex.writePackIndex(result.objects,
  
positive.code: class Clone {
    PrintProfiler _stopwatch;
  
    GitOptions _options;
  
    Clone(this._options) {
  
negative.code:     if (_options.progressCallback == null) {
        _options.progressCallback = nopFunction;
      }
  
      cancel = new CloneCancel();
    }
  
    chrome.DirectoryEntry get root => _options.root;
  