bug#60592: 30.0.50; emacsclient: exit with a different code when the request times out

[Eli Zaretskii]

> From: Sean Whitton <spwhitton@spwhitton.name>
> Cc: 60592@debbugs.gnu.org
> Date: Fri, 06 Jan 2023 10:57:18 -0700
> 
> Hello,
> 
> On Fri 06 Jan 2023 at 09:37AM +02, Eli Zaretskii wrote:
> 
> >> From: Sean Whitton <spwhitton@spwhitton.name>
> >> Date: Thu, 05 Jan 2023 22:47:49 -0700
> >>
> >> When calling 'emacsclient --timeout N --eval' from scripts, it would be
> >> nice if you could determine for sure when a failure was just due to a
> >> timeout, rather than, say, a Lisp exception.
> >>
> >> inotifywait(1) exits with code 2 to indicate a timeout.
> >> emacsclient could do the same.
> >
> > It would be more portable to have the exception handler send a special
> > message to emacsclient, so that it would know the reason without
> > guessing.
> 
> I think this is wholly complimentary to what I'm suggesting, right?

I didn't think so, but maybe I was missing something.

My point is that if we make the exception known to emacsclient, then
when the timeout ends without exceptions, it should be clear it was a
real timeout.