anchor.diff:        '### ${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)));
   }
  
positive.code:       ..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');
      try {
        _results = _parser.parse(args);
        if (_results['help']) _printUsage();
  
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',
  