@NotNull
  VirtualFileSystemEntry getOrCacheDir(@NotNull VirtualFileSystemEntry newDir) {
    int id = newDir.getId();
    ConcurrentIntObjectMap<VirtualFileSystemEntry> cache = getCache(newDir);
    VirtualFileSystemEntry dir = cache.get(id);
    if (dir != null) return dir;
    return cache.cacheOrGet(id, newDir);
  }
@NotNull
  VirtualFileSystemEntry getOrCacheDir(@NotNull VirtualFileSystemEntry newDir)