anchor.diff:        ..addOption('to',
             defaultsTo: DateTime.now().toIso8601String(),
             abbr: 't',
  -          help: 'to date, ISO format yyyy-mm-dd')
  -      ..addOption('exclude-performance',
  -          abbr: 'e', help: 'include performance issues');
  +          help: 'to date, ISO format yyyy-mm-dd');
       try {
         _results = _parser.parse(args);
         if (_results['help']) _printUsage();
  
positive.code:       '### ${closedThisPeriod.length} `P0` issue(s) closed between ${fromStamp} and ${toStamp}');
    closedThisPeriod.forEach((issue) =>
        print(issue.summary(boldInteresting: false, linebreakAfter: true)));
  
    // Bail if we don't care about performance issues.
    if (opts.excludePerformance) return;
  
    // Now do the same for performance issues.
    var openPerfIssues = await github.search(
      owner: 'flutter',
      name: 'flutter',
      type: GitHubIssueType.issue,
      state: GitHubIssueState.open,
      labels: ['severe: performance'],
    );
  
    var closedPerfIssues = await github.fetch(
      owner: 'flutter',
      name: 'flutter',
      type: GitHubIssueType.issue,
      state: GitHubIssueState.closed,
      labels: ['severe: performance'],
    );
  
    open = List<Issue>();
    openedThisPeriod = List<Issue>();
    closedThisPeriod = List<Issue>();
  
    openPerfIssues.forEach((issue) {
      if (issue.state == "OPEN") open.add(issue);
      if (issue.createdAt.compareTo(opts.from) >= 0 &&
          issue.createdAt.compareTo(opts.to) <= 0) openedThisPeriod.add(issue);
    });
  
    closedPerfIssues.forEach((issue) {
      if (issue.state == "CLOSED" &&
          issue.closedAt.compareTo(opts.from) >= 0 &&
          issue.closedAt.compareTo(opts.to) <= 0) closedThisPeriod.add(issue);
      if (issue.createdAt.compareTo(opts.from) >= 0 &&
          issue.createdAt.compareTo(opts.to) <= 0) openedThisPeriod.add(issue);
    });
  
    printHeader(opts, 'performance');
  
    print(
        'This shows the number of new, open, and closed `severe: performance` issues over the period from');
    print('${fromStamp} to ${toStamp}.\n\n');
  
    print('### ${open.length} open `severe: performance` issue(s) in total\n');
  
    print(
        '### ${openedThisPeriod.length} `severe: performance` issue(s) opened between ${fromStamp} and ${toStamp}');
    openedThisPeriod.forEach((issue) =>
        print(issue.summary(boldInteresting: false, linebreakAfter: true)));
  
    print(
        '### ${closedThisPeriod.length} `severe: performance` issue(s) closed between ${fromStamp} and ${toStamp}');
    closedThisPeriod.forEach((issue) =>
        print(issue.summary(boldInteresting: false, linebreakAfter: true)));
  }
  
negative.code:   DateTime get from => DateTime.parse(_results['from']);
    DateTime get to => DateTime.parse(_results['to']);
    int get exitCode => _results == null ? -1 : _results['help'] ? 0 : null;
    Options(List<String> args) {
      _parser
        ..addFlag('help',
  