docs: function dirInstall(dirpath, callback) {
    callback = utils.defineCallback(callback);
    return fs.exists(dirpath, function(exists) {
      if (!exists) {
        return callback(new errors.DirectoryNotExistingError());
      }
      var pluginName = path.basename(dirpath);
      var destPath = path.join(pluginsDir, pluginName);
      return ncp(dirpath, destPath, function(copyError) {
        if (copyError) {
          return callback(new errors.PluginsMoveFromTempError(copyError));
        }
        return callback(null);
      });
    });
  }