bug#62845: 29.0.90; nntp-with-open-group-function kills current buffer on timeout

[Eli Zaretskii <eliz@gnu.org>]

> From: Eric Abrahamsen <eric@ericabrahamsen.net>
> Cc: schwab@linux-m68k.org,  62845@debbugs.gnu.org
> Date: Fri, 05 May 2023 17:03:35 -0700
> 
> `nntp-report' used to raise an error in this case, so it didn't matter
> what happened afterwards. That error would derail the entire process of
> Gnus checking for news/mail, so I took it out so that other servers
> could continue doing their work even if this one had lost its
> connection.
> 
> But then the current buffer of `with-current-buffer` is gone, which as
> Andreas notes dumps us in the most-recently-used buffer, which could be
> anything. The `nnheader-strip-cr' acts on that buffer, and terrible
> things result.
> 
> Other code in this library checks if the timer has killed the process
> buffer in the meantime. There's probably a safe solution in here
> somewhere, but if you're looking for a reliable regression fix to
> include in Emacs 29, it's probably best just to revert 032969e8c65. That
> behavior is annoying, but at least not buggy.
> 
> WDYT?

Fine with me, but what is the plan for master?  If you can show the
proposed solution for master, we could then try to figure out if it is
safe enough for emacs-29 as well.

But if it will take a significant time to come up with such a solution
for master, then let's revert on emacs-29 for now.

Thanks.