anchor.diff:        abbr: 'o',
         help: 'Output file.',
         defaultsTo: null)
  +  ..addFlag('verbose',
  +      abbr: 'v',
  +      negatable: false,
  +      help: 'Be verbose (e.g. prints transformed main library).',
  +      defaultsTo: false)
     ..addOption('transformation',
         abbr: 't',
         help: 'The transformation to apply.',
  
positive.code:   var input = result.rest.first;
    var output = result['out'];
    var format = result['format'];
  
    if (output == null) {
      output = '${input.substring(0, input.lastIndexOf('.'))}.transformed.dill';
  
negative.code:     writeProgramToBinary(program, output);
    }
  
    if (verbose) {
      writeLibraryToText(program.mainMethod.parent as Library, null);
    }
  }
  