anchor.diff:                .where((name) => !mixins.containsKey(name)),
               (name) => transform
                 .getInput(new AssetId(transform.primaryInput.id.package,
  -                  '${_prefixFrom(transform.primaryInput.id)}$path/name.dart'))
  +                  '${_prefixFrom(transform.primaryInput.id)}$path/$name.dart'))
                 .then((asset) => asset.read())
                 .then((byteStream) => byteStream.pipe(
                     new mixologist.MixinReader()))
  
positive.code:         transform.addOutput(new Asset.fromString(id, lines.join('\n')));
        })
      );
    }
  }
  
  String _prefixFrom(AssetId asset) => (asset.path.split('/')..removeLast()..add('')).join('/');
negative.code:   
    String get allowedExtensions => '.mixologist.yaml';
      
    Future apply(Transform transform) =>
      transform
        .primaryInput
        .readAsString()
        .then(yaml.loadYaml)
  