docs: function merge(options) {
      assert.ok(options.branch, 'branch is mandatory');
      assert.ok(options.message, 'message is mandatory');
  
      var args = [
        'merge',
        options.noFF ? '--no-ff' : null,
        options.remote ? (options.remote + '/' + options.branch) : options.branch,
        '-m',
        options.message
      ];
  
      return git(args)
          .then(silent);
    }