@Nullable
  private VcsCacheableHistorySessionFactory<Serializable, VcsAbstractHistorySession> getCacheableFactory() {
    if (!(myHistoryProvider instanceof VcsCacheableHistorySessionFactory)) return null;
    //noinspection unchecked
    return (VcsCacheableHistorySessionFactory<Serializable, VcsAbstractHistorySession>)myHistoryProvider;
  }
@Nullable
  private VcsCacheableHistorySessionFactory<Serializable, VcsAbstractHistorySession> getCacheableFactory()