code: private FileFilter createConfigFilesFilter() {
          SiteConfig config = site.getConfig();
          boolean useDefaultConfigFiles = config.useDefaultConfigFiles();
          if (useDefaultConfigFiles) {
              log.debug("Using default config files.");
              return SiteConfigImpl.DEFAULT_CONFIG_FILES_FILTER;
          } else {//custom config files
              final File[] configFiles = config.getConfigFiles();
              return new FileFilter() {
                  @Override
                  public boolean accept(File file) {
                      for (File configFile : configFiles) {
                          if (configFile.equals(file)) {
                              return true;
                          }
                      }
                      return false;
                  }
              };
          }
      }
docs: Create config files FileFilter.
  
  @return file filter