code: function overrideConfig(config) {
      if (fs.existsSync(config.config)) {
          var content = fs.readFileSync(config.config, {
              encoding: "utf8"
          });
          var configFile = JSON.parse(content);
          for (var key in configFile) {
              if (configFile.hasOwnProperty(key)) {
                  config[key] = configFile[key];
              }
          }
      }
      return config;
  }
docs: Config options override.