anchor.diff:        for (var label in toRemove) clusters.remove(label);
       }
   
  +    if (opts.labels && opts.skipUninteresting) {
  +      Set<String> toRemove = Set<String>();
  +      for (var label in clusters.clusters.keys) {
  +        if (labelsToSkip.contains(label)) toRemove.add(label);
  +      }
  +      for (var label in toRemove) clusters.remove(label);
  +    }
  +
       print(clusters.toMarkdown(
           sortType: (opts.alphabetize
               ? ClusterReportSort.byKey
  
positive.code:           abbr: 'l',
            negatable: false,
            help: 'cluster by label')
        ..addFlag('authors',
            defaultsTo: false,
            abbr: 'a',
  
negative.code: 
    void _printUsage() {
      print(
          'Usage: pub run clusters.dart [--labels] [--skip-uninteresting-labels] [--authors] [--assignees] [--prs] [--issues] [--merged fromDate toDate] [--closed fromDate toDate]');
      print('Prints PRs in flutter/flutter, flutter/engine repositories.');
      print('  Dates are in ISO 8601 format');
      print('  --merged and --closed are mutally exclusive');
  