anchor.diff:  import 'package:ddc/src/checker/dart_sdk.dart' show dartSdkDirectory, mockSdkSources;
   import 'package:ddc/src/checker/resolver.dart' show TypeResolver;
   
  -ArgResults parse(List argv) {
  -  var parser = new ArgParser()
  +final ArgParser argParser = new ArgParser()
       ..addFlag(
           'sdk-check', abbr: 's', help: 'Typecheck sdk libs', defaultsTo: false)
       ..addOption('log', abbr: 'l', help: 'Logging level', defaultsTo: 'severe')
  
positive.code: 
    if (args.rest.length == 0) {
      print('Expected filename.');
      exit(1);
    }
  
    String levelName = args['log'].toUpperCase();
  
negative.code:         'mock-sdk', abbr: 'm', help: 'Use a mock Dart SDK', defaultsTo: false)
      ..addFlag('new-checker', abbr: 'n', help: 'Use the new type checker',
          defaultsTo: false)
      ..addOption('out', abbr: 'o', help: 'Output directory', defaultsTo: null)
      ..addFlag('help', abbr: 'h', help: 'Display this message');
  
  void _showUsageAndExit() {
    print('usage: dartdevc [<options>] <file.dart>\n');
    print('<file.dart> is a single Dart file to process.\n');
    print('<options> include:\n');
    print(argParser.usage);
    exit(1);
  }
  
  int main(List<String> argv) {
    ArgResults args = argParser.parse(argv);
    if (args['help']) _showUsageAndExit();
  
    bool shouldMockSdk = args['mock-sdk'];
    String dartSdkPath;
    if (!shouldMockSdk) {
  