anchor.diff:        ..addFlag('labels', defaultsTo: false, abbr: 'l', negatable: false, help: 'cluster by label')
         ..addFlag('authors', defaultsTo: false, abbr: 'a', negatable: false, help: 'cluster by authors')
         ..addFlag('prs', defaultsTo: false, abbr: 'p', negatable: false, help: 'cluster pull requests')
  -      ..addFlag('issues', defaultsTo: false, abbr: 'i', negatable: false, help: 'cluster issues');
  +      ..addFlag('issues', defaultsTo: false, abbr: 'i', negatable: false, help: 'cluster issues')
  +      ..addFlag('alphabetize', defaultsTo: false, abbr: 'z', negatable: true, help: 'sort labels alphabetically')
  +      ..addFlag('customers-only', defaultsTo: false, abbr: 'c', negatable: true, help: 'for labels, show only labels with `customer:`');
       try {
         _results = _parser.parse(args);
         if (_results['help'])  _printUsage();
  
positive.code:   bool get authors => _results['authors'];
    bool get prs => _results['prs'];
    bool get issues => _results['issues'];
    int get exitCode => _results == null ? -1 : _results['help'] ? 0 : null;
  
    Options(List<String> args) {
  
negative.code: void main(List<String> args) async {
    final opts = Options(args);
    if (opts.exitCode != null) exit(opts.exitCode);
    Set<String> keys = Set<String>();
  
    var repos = opts.prs ? ['flutter', 'engine'] : ['flutter'];
  
  