bug#60245: 28.2; recentf: Be able to include directories

[Drew Adams]

> > Enhancement request: Have recentf let you optionally include
> > directories that you've visited with Dired.  (Currently it
> > seems that the gatekeeper in the code is basically `buffer-file-name'.)
> 
> FWIW I use the following, suggested long ago by Kevin Rodgers
> (https://urldefense.com/v3/__https://lists.gnu.org/archive/html/help-gnu-
> emacs/2004-01/msg00525.html__;!!ACWV5N9M2RV99hQ!I8OUv_4GGpM-NU-4syprdTz-
> kiCHPePv0_de0Qgr9k0Axdiq5SN8f0uZupnV6t2yCPad_Bd5BDeQQRQ83IrUJ281$ ):
> 
> (add-hook 'dired-mode-hook
>         (lambda () (when recentf-mode
>                         (recentf-add-file default-directory))))

Good idea. Thx.

Governing that with a user option might be a good idea.
That is, do that systematically, whenever the option
says so, rather than having users opt in by adding such
a hook function.