anchor.diff:  /** Copy a file from [inpath] to [outpath]. */
   Future _copyFile(String inpath, String outpath) {
     _ensureDir(path.dirname(outpath));
  -  var writer = new File(outpath).openWrite();
  -  return writer.addStream(new File(inpath).openRead())
  -      .then((_) => writer.close());
  +  return new File(inpath).openRead().pipe(new File(outpath).openWrite());
   }
   
   /** Write contents of an [asset] into a file at [filepath]. */
   Future _writeAsset(String filepath, Asset asset) {
     _ensureDir(path.dirname(filepath));
  -  var writer = new File(filepath).openWrite();
  -  return writer.addStream(asset.read()).then((_) => writer.close());
  -}
  +  return asset.read().pipe(new File(filepath).openWrite());
  +}
  
positive.code:   var currentPackage = options.currentPackage;
    var transformTests = options.transformTests;
    var outPackages = path.join(options.outDir, 'packages');
    for (var asset in assets) {
      var id = asset.id;
      var dir = _firstDir(id.path);
      if (dir == null) continue;
  
      var filepath;
      if (dir == 'lib') {
  
negative.code:       filepath = path.join(options.outDir, _toSystemPath(id.path));
      } else {
        // TODO(sigmund): do something about other assets?
        return null;
      }
  
      return _writeAsset(filepath, asset);
    });
  }
  
  /**
  