anchor.diff:    }
   
     var args = [
  +    if (_noUnknownKeyword) "--warning=no-unknown-keyword",
       "--extract",
       "--gunzip",
       "--no-same-owner",
  
positive.code: 
  /// Whether to include "--warning=no-unknown-keyword" when invoking tar.
  ///
  /// This flag quiets warnings that come from opening OS X-generated tarballs on
  /// Linux, but only GNU tar >= 1.26 supports it.
  final bool _noUnknownKeyword = _computeNoUnknownKeyword();
  bool _computeNoUnknownKeyword() {
    if (!Platform.isLinux) return false;
  
negative.code:     "--directory",
      destination
    ];
  
    var process = await _startProcess("tar", args);
  
  