code: public void addLoggerRepositoryEventListener(
      final LoggerRepositoryEventListener listener) {
      synchronized (repositoryEventListeners) {
        if (repositoryEventListeners.contains(listener)) {
          LogLog.warn(
            "Ignoring attempt to add a previously "
                    + "registered LoggerRepositoryEventListener.");
        } else {
          repositoryEventListeners.add(listener);
        }
      }
    }
docs: Add a {@link LoggerRepositoryEventListener} to the repository. The
  listener will be called when repository events occur.
  @param listener listener