bug#47119: 28.0.50; [patch][Dired] new user option for compressing dir suffix

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 22 Mar 2021 20:28:48 +0800
> From: LinSun <lin.sun@zoom.us>
> Cc: "47119@debbugs.gnu.org" <47119@debbugs.gnu.org>, 
> 	"sunlin7@yahoo.com" <sunlin7@yahoo.com>
> 
> >> -    ("\000" ".tar.gz" "tar -cf - %i | gzip -c9 > %o"))
> 
> >Why did you remove the "\000" entry?  As the comment explains, it is
> 
> >there to allow compressing a directory.  To compress a directory, you
> 
> >need to run 'tar' on it first, and the .tar.gz/.tar.xz entries run
> 
> >'tar' on the _result_ of gzip/xz instead.  So how will compression of
> 
> >directories work after your changes?  I feel that I'm missing
> 
> >something here, but what?
> 
> The “\000” entry is special for compress directory, if you go through back, other entries in the
> `dired-compress-file-suffixes` is decompress commands. After apply this patch, the “\000” entry is useless.

I'm still missing something, I think.  Please describe step by step
how compressing a directory will work after your changes, and in
particular what shell command(s) will Dired run in that case.

Thanks.