anchor.diff:  import 'package:csv/csv.dart';
   import 'dart:io';
   
  -
  -
  -class Options  {
  +class Options {
     final _parser = ArgParser(allowTrailingOptions: false);
     ArgResults _results;
     bool get showClosed => _results['closed'];
  
positive.code: 
    Options(List<String> args) {
      _parser
        ..addFlag('help', defaultsTo: false, abbr: 'h', negatable: false, help: 'get usage')
        ..addFlag('closed', defaultsTo: false, abbr: 'c', negatable: false, help: 'show punted issues in date range')
        ..addFlag('merged', defaultsTo: false, abbr: 'm', negatable: false, help: 'show merged PRs in date range');
      try {
        _results = _parser.parse(args);
        if (_results['help'])  _printUsage();
        if ((_results['closed'] || _results['merged']) && _results.rest.length != 2 ) throw('need start and end dates!');
        if (_results['merged'] && _results['closed']) throw('--merged and --closed are mutually exclusive!');
      } on ArgParserException catch (e) {
        print(e.message);
        _printUsage();
  
negative.code:   DateRange when = null;
    var rangeType = GitHubDateQueryType.none;
    if (opts.showClosed || opts.showMerged) {
      state = opts.showClosed ? GitHubIssueState.closed : GitHubIssueState.merged;
      when = DateRange(DateRangeType.range, start: opts.from, end: opts.to);
      rangeType = GitHubDateQueryType.closed;
    }
  
    var prs = List<dynamic>();
    for (var repo in repos) {
      prs.addAll(await github.search(
          owner: 'flutter',
          name: repo,
          type: GitHubIssueType.pullRequest,
          state: state,
          dateQuery: rangeType,
          dateRange: when));
    }
  
    var reportType = 'oen';
    if (opts.showMerged) reportType = 'merged';
    if (opts.showClosed) reportType = 'closed';
  
    print(opts.showClosed || opts.showMerged
        ? "# Non-Google contributors contributing ${reportType} PRs from " +
            opts.from.toIso8601String() +
            ' to ' +
            opts.to.toIso8601String()
        : "# Non-Google contributors contributing ${reportType} PRs");
  
    if (false) {
      print('## All issues\n');
  