bug#44644: /tmp/emacs0/ not cleaned up upon exit

[Jean Louis <bugs@gnu.support>]

* Eli Zaretskii <eliz@gnu.org> [2020-11-27 11:13]:
> > From: Lars Ingebrigtsen <larsi@gnus.org>
> > Cc: jidanni@jidanni.org,  44644@debbugs.gnu.org
> > Date: Fri, 27 Nov 2020 08:48:30 +0100
> > 
> > Eli Zaretskii <eliz@gnu.org> writes:
> > 
> > > At most, yes.  The problem is, it isn't easy to know when the
> > > directory is under /tmp (we don't use temporary-file-directory, for
> > > the reasons explained in the comment to server-socket-dir).  Maybe we
> > > should put some special property on server-dir when that is the case?
> > 
> > Did you mean server-socket-dir instead of server-dir here?
> 
> Yes, sorry.
> 
> > Yes, I guess that'd be possible, but the user may change
> > server-socket-dir without changing the property...
> > 
> > We could literally just check whether the parent of server-socket-dir is
> > "/tmp" and only delete then.  It'd be pretty defensive, but should fix
> > this minor annoyance.
> 
> If no better ideas come to mind, yes.
> 
> I actually don't share the feeling of an annoyance here: /tmp is
> regularly cleaned up anyway, right?  But that's me.

Many applications that use some directory in /tmp leave directories
there. It should be cleaned up by system on next run.

If users can customize directory place they could use all kinds of
parent directory names

And if directory should be deleted, then such should be checked not to
contain any other file that could be placed in directory.

Recently when running debugging various .heap and mtrace files are all
over the system. If directory is inspected by Emacs under debugging,
some files would be placed there automatically.