anchor.diff:  main(List<String> args) {
   
     var parser = new ArgParser();
  -  parser.addOption('dir', abbr:'d');
  -  parser.addOption('group', abbr:'g');
  +  parser.addOption('in',    abbr: 'i');
  +  parser.addOption('out',   abbr: 'o');
  +  parser.addOption('group', abbr: 'g');
   
     var results = parser.parse(args);
   
  -  if(results['dir'] != null) {
  -    rootDir = new Directory(results['dir']);
  +  if(results['in'] != null) {
  +    rootDir = new Directory(results['in']);
     } else {
       rootDir = Directory.current;
     }
  
positive.code:   } else {
  
      List<FileSystemEntity> targetFs = new List();
  
      results['group'].split(',').forEach((dt) {
        targetFs.addAll(parseDirectory(dt));
      });
  
negative.code:   }
  
    csvResult.then((String csv) {
  
      File exportFile;
  
      if(results['out'] == null) {
        exportFile = new File(rootDir.path + '/export.csv');
      } else if(results['out'][0] == '/' || results['out'][0] == '~') {
        exportFile = new File(results['out']);
      } else {
        exportFile = new File(rootDir.path + '/' + results['out']);
      }
      exportFile.writeAsStringSync(csv);
      print('');
      print('complete!');
  