anchor.diff:    ..addOption('exclude-pattern',
         help: 'regular expression of file names to exclude', defaultsTo: null)
     ..addOption('dart-sdk', help: 'Dart SDK Path', defaultsTo: null)
  +  ..addOption('package-root',
  +      abbr: 'p',
  +      help: 'Package root to resolve "package:" imports',
  +      defaultsTo: 'packages/')
  +  ..addFlag('use-multi-package',
  +      help: 'Whether to use the multi-package resolver for "package:" imports',
  +      defaultsTo: false)
  +  ..addOption('package-paths', help: 'if using the multi-package resolver, '
  +      'the list of directories where to look for packages.', defaultsTo: '')
     ..addFlag('help', abbr: 'h', help: 'Display this message');
   
   void _showUsageAndExit() {
  
positive.code:   }
  
    var filename = args.rest.first;
    var typeResolver =
        new TypeResolver.fromDir(sdkDir.path, new ResolverOptions());
  
    Map json = JSON.decode(new File(filename).readAsStringSync());
    var summary = GlobalSummary.parse(json);
  
negative.code: import 'package:source_maps/refactor.dart';
  import 'package:source_span/source_span.dart';
  
  import 'package:ddc/src/options.dart';
  import 'package:ddc/src/report.dart';
  import 'package:ddc/src/checker/resolver.dart' show TypeResolver;
  
  