dired-guess-shell-alist-user: How to match folders instead of file types?

[Marius Hofert]

Hi,

I use ...

(setq dired-guess-shell-alist-user
      '(("\\.zip\\'" "(unzip ? &>/dev/null &)")
("\\.tar.gz\\'" "(tar xzf ? &>/dev/null &)")))

... to execute the corresponding command from dired-mode (on
M-!).  I am wondering how one can match *folders* (in contrast to
file types such as .zip, .tar.gz), such that M-! suggests a
command to be executed on folders?

Cheers,

Marius