code: protected String getIndexDirParam() throws RepositoryConfigurationException
     {
        String dir = config.getParameterValue(QueryHandlerParams.PARAM_INDEX_DIR, null);
        if (dir == null)
        {
           LOG.warn(QueryHandlerParams.PARAM_INDEX_DIR + " parameter not found. Using outdated parameter name "
              + QueryHandlerParams.OLD_PARAM_INDEX_DIR);
           dir = config.getParameterValue(QueryHandlerParams.OLD_PARAM_INDEX_DIR);
        }
        return dir;
     }
docs: ^
  Returns "index-dir" parameter from configuration.