anchor.diff:    }
   
     Future _detectOldVersion() async {
  -    final pr = await Process.run(
  -      'gcloud',
  -      ['app', 'versions', 'list', '--service', service, '--format=value(id)'],
  +    final pr = await _runGCloudApp(
  +      ['versions', 'list', '--service', service, '--format=value(id)'],
       );
       if (pr.exitCode != 0) {
         print('[ERR] Couldn\'t detect old $service version.');
  
positive.code: 
    Future _gcloudDeploy() async {
      final String yamlFile = service == 'default' ? 'app.yaml' : '$service.yaml';
      final pr = await Process.run(
        'gcloud',
        ['app', 'deploy', yamlFile, '--no-promote', '-v', newVersion, '-q'],
      );
      if (pr.exitCode != 0) {
        print('[ERR] Couldn\'t deploy $service.');
  
negative.code: 
    Future _deleteOldVersion() async {
      if (_oldVersion == null) return;
      final pr = await _runGCloudApp(
          ['versions', 'delete', '--service', service, _oldVersion, '-q']);
      if (pr.exitCode != 0) {
        print('[ERR] Couldn\'t delete old version of $service.');
        print(pr.stderr);
        exit(1);
      }
    }
  
    Future<ProcessResult> _runGCloudApp(List<String> args) => Process.run(
        'gcloud',
        [
          '--project',
          project,
          'app',
        ]..addAll(args));
  }
  