bug#48072: 28.0.50: dired-read-shell-command: handle empty input properly [PATCH]

[Eli Zaretskii]

> Date: Tue, 27 Apr 2021 15:02:43 -0400
> From: Boruch Baum <boruch_baum@gmx.com>
> 
> Function dired-read-shell-command was accepting an empty input. This is
> a bug because it then passes the empty input as a legitimate command
> which is silently processed (in error) by dired, eventually to return a
> completion message.

I'm not sure we want to disallow this.  (Wasn't there a similar
discussion recently?)

> validates the entered command as a valid shell executable.

This is certainly a mistake: a valid shell command doesn't have to be
a file that executable-find is able to find.  Shells are known to
support all kinds of internal and magic commands.

Thanks.