anchor.diff:  }
   
   main([List<String> args]) {
  -  ArgParser parser = new ArgParser();
  -  parser.addOption(
  -      'output',
  +  ArgParser parser = ArgParser();
  +  parser.addOption('output',
         abbr: 'o',
         help: 'Output file for tags (default: stdout)',
         valueHelp: 'FILE');
  -  parser.addFlag('follow-links', help: 'Follow symbolic links (default: false)', negatable: false);
  -  parser.addFlag(
  -      'include-hidden',
  -      help: 'Include hidden directories (default: false)',
  -      negatable: false);
  -  parser.addFlag(
  -      'line-numbers',
  +  parser.addFlag('follow-links',
  +      help: 'Follow symbolic links (default: false)', negatable: false);
  +  parser.addFlag('include-hidden',
  +      help: 'Include hidden directories (default: false)', negatable: false);
  +  parser.addFlag('line-numbers',
         abbr: 'l',
         help: 'Add line numbers to extension fields (default: false)',
         negatable: false);
  -  parser.addFlag('skip-sort', help: 'Skip sorting the output (default: false)', negatable: false);
  +  parser.addFlag('skip-sort',
  +      help: 'Skip sorting the output (default: false)', negatable: false);
     parser.addFlag('help', abbr: 'h', help: 'Show this help', negatable: false);
     ArgResults options = parser.parse(args);
     if (options['help']) {
  
positive.code:     }
  
      List<String> lines = [
          '!_TAG_FILE_FORMAT\t2\t/extended format; --format=1 will not append ;" to lines/',
          '!_TAG_FILE_SORTED\t1\t/0=unsorted, 1=sorted, 2=foldcase/'];
  
      Future.wait(dirs.map(addFileSystemEntity)).then((Iterable<Iterable<Iterable<String>>> files) {
        files.forEach((Iterable<Iterable<String>> file) {
          file.forEach((Iterable<String> fileLines) => lines.addAll(fileLines));
        });
  
negative.code:     FileSystemEntityType type = FileSystemEntity.typeSync(name);
  
      if (type == FileSystemEntityType.DIRECTORY) {
        return Directory(name)
            .list(recursive: true, followLinks: options['follow-links'])
            .map((file) {
          if (file is File && path.extension(file.path) == '.dart') {
            return parseFile(file);
          } else {
  