bug#54296: Add buffer-matching functionality

[Eli Zaretskii]

> Date: Mon, 13 Jun 2022 03:21:13 +0300
> Cc: 54296@debbugs.gnu.org, larsi@gnus.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> 
> On 14.03.2022 15:38, Philip Kaludercic wrote:
> > The issue isn't that the default value couldn't be updated, but that if
> > anyone has e.g. been using `project-kill-buffer-conditions' over the
> > last 1½ years and has relied on the specific distinction between
> > `major-mode' and `derived-mode', they would run in to unexpected
> > results, that might result in more buffers being killed than intended,
> > potentially data being lost that the user might not expect because of an
> > update.
> 
> I see that this point hasn't been addressed at all.
> 
> Eli?

Do you agree with Philip that deprecating or removing major-mode would
be a problem for users of project-kill-buffer-conditions etc.?

I kinda gave up because Philip felt extremely uneasy with dropping
major-mode, leaving us with just derived-mode, but I still think we
shouldn't encourage Lisp programs to use major-mode.  So if you don't
think it would be a problem, I'd be happier if we removed major-mode
and used derived-mode instead.