anchor.diff:    var includeSdk = results['parse-sdk'] || results['include-sdk'];
     var scriptDir = path.dirname(Platform.script.toFilePath());
     var introduction = includeSdk ? '' : results['introduction'];
  -  docgen(results.rest.map(path.normalize).toList(),
  +  var files = results.rest.map(path.normalize).toList();
  +  if (files.isEmpty) _printHelpAndExit();
  +  docgen(files,
         packageRoot: results['package-root'],
         outputToYaml: !results['json'],
         includePrivate: results['include-private'],
  
positive.code: }
  
  /**
   * Creates parser for docgen command line arguments.
   */
  ArgParser _initArgParser() {
  
negative.code:       help: 'Prints help and usage information.',
        negatable: false,
        callback: (help) {
          if (help) _printHelpAndExit();
        });
    parser.addFlag('verbose', abbr: 'v',
        help: 'Output more logging information.', negatable: false,
  