anchor.diff:  }
   
   void parseCommandLine(List<OptionHandler> handlers, List<String> argv) {
  +  // TODO(ahe): Use ../../args/args.dart for parsing options instead.
     var patterns = <String>[];
     for (OptionHandler handler in handlers) {
       patterns.add(handler.pattern);
  
positive.code:   // terminal size normally 80x24. Two lines are used for the prompts
    // before and after running the compiler.
    print('''
  Usage: dart2js [OPTIONS] DARTFILE
  
  Compiles Dart to JavaScript.
  
  Common options:
    --help      Display this message.
    --out=FILE  Save the output to FILE (default: out.js).
    --checked   Turn on checked mode in generated JavaScript code.''');
  }
  
  void helpAndExit() {
    help();
    exit(0);
  }
  
  
negative.code: 
    parseCommandLine(handlers, argv);
  
    if (wantHelp) helpAndExit(verbose);
  
    if (arguments.isEmpty()) {
      helpAndFail('Error: No Dart file specified.');
    }
  