docs: function tag(options) {
      assert.ok(options.tag, 'tag name is mandatory');
      if (options.annotated) {
        assert.ok(options.message, 'message is mandatory when creating an annotated tag');
      }
  
      var args = [
        'tag',
        options.tag,
        options.annotated ? '-a' : null,
        options.message ? '-m' : null,
        options.message ? options.message : null
      ];
  
      return git(args)
          .then(silent);
    }