anchor.diff:  import 'dart:io';
   import 'dart:mirrors';
   
  -import 'package:args/args.dart' show ArgParser;
  +import 'package:args/args.dart';
   import 'package:collection/collection.dart';
   import 'package:html/dom.dart' as dom;
   import 'package:html/parser.dart' show parseFragment;
  
positive.code:   var updateFiles = options['update-files'] as bool;
  
    if (updateFiles && (raw || verbose || (specifiedSection != null))) {
      print('The `update-files` flag must be used by itself');
      print(parser.usage);
      exitCode = 64; // unix standard improper usage
      return;
  
negative.code:         defaultsTo: false, help: 'verbose output', negatable: false)
      ..addFlag('help', defaultsTo: false, negatable: false);
  
    ArgResults options;
  
    try {
      options = parser.parse(args);
    } on FormatException catch (e) {
      stderr.writeln(e);
      print(parser.usage);
      exitCode = 64;
      return;
    }
  
    if (options['help']) {
      print(parser.usage);
  