bug#65267: 30.0.50; modifying debug-ignored-errors during startup with --debug-init is broken

[Eli Zaretskii]

> From: Štěpán Němec <stepnem@smrk.net>
> Cc: 65267@debbugs.gnu.org, npostavs@users.sourceforge.net
> Date: Thu, 17 Aug 2023 16:16:19 +0200
> 
> On Thu, 17 Aug 2023 16:28:31 +0300
> Eli Zaretskii wrote:
> 
> >> From: Stefan Monnier <monnier@iro.umontreal.ca>
> >> Cc: stepnem@smrk.net,  65267@debbugs.gnu.org,  
> >> npostavs@users.sourceforge.net
> >> Date: Thu, 17 Aug 2023 08:55:38 -0400
> >> 
> >> > What about the minor changes below?  They do seem to yield the
> >> > expected results in the original recipe.  The idea is to detect the
> >> > situation where the init file _added_ to the value of
> >> > debug-ignored-errors, and re-add the additions after loading the init
> >> > file.
> >> 
> >> No objection from me (it's not great, but I don't think there's a great
> >> solution).
> >
> > Thanks.
> >
> > Štěpán, would you mind testing the patch?  If it works for you, I will
> > install it.
> 
> Your patch preserves additions (although it moves them to the end of the
> list, but that shouldn't matter for debug-ignored-errors), but doesn't
> preserve removals

If someone want to remove from the list, and use --debug-init on top
of that, they will need to replace the value instead.  If that's the
only downside of the patch I proposed, I think people will be able to
live with it.

> Have you considered my humble suggestion of reverting to pre-bug#64163
> state and simply removing end-of-file from the default value of
> debug-ignored-errors?

Yes.  This cannot fly, since we had end-of-file there for a long time
(I see it in Emacs 20).