recentf ignores directory

[Tak Ota]

I don't find a way to customize recentf to remember opened directory
names as well as file names.  So I have the following customization in
my .emacs.  Don't you think it is generally useful if the recentf
remembers directory names as well?

  (defun recentf-track-opened-directory (dir)
    "Insert the name of the directory just opened into the recent list."
    (recentf-add-file dir)
    nil)
  (add-to-list 'recentf-used-hooks '(find-directory-functions 
recentf-track-opened-directory))

-Tak

I don't subscribe to the emacs-devel list so please include the
address explicitly for the correspondence.