code: function(cb) {
              var lockFile = path.join(repoDir, '.git', 'index.lock');
              path.exists(lockFile, function(exists) {
                  if (exists) {
                      fs.unlink(lockFile, function(err) {
                          if (err) {
                              log.warn('removing file ' + lockFile + ' failed with:', err);
                          }
                          else {
                              log.info('removed lock file: ' + lockFile);
                          }
                          cb(err, {removelock: 'remove git lock ' + lockFile + ', result ' + err});
                      });
                      return;
                  }
                  log.log('There is no lock file left, which is a good thing');
                  cb(null, {removelock: 'no lock was present'});
              });
          }
docs: Remove git lock file to recover if git operation was aborted during previous run.