Status DeleteRecursively(const std::string& dirname, TransactionToken* token,
                           int64_t* undeleted_files,
                           int64_t* undeleted_dirs) override;
  Status DeleteDir(const std::string& dirname,
                   TransactionToken* token) override;
  Status RecursivelyCreateDir(const std::string& dirname,

  /// and `*undeleted_dirs` must be 0. On unsuccessful deletion, `status` must
  /// be set to the reason why one entry couldn't be removed and the proper
  /// count must be updated. If the deletion is unsuccessful because the
  /// traversal couldn't start, `*undeleted_files` must be set to 0 and
  /// `*undeleted_dirs` must be set to 1.
  ///