bug#54296: Add buffer-matching functionality

[Eli Zaretskii]

> From: Philip Kaludercic <philipk@posteo.net>
> Cc: larsi@gnus.org,  54296@debbugs.gnu.org
> Date: Thu, 10 Mar 2022 12:13:59 +0000
> 
> > Do we really need both major-mode and derived-mode?
> 
> It seems to have been useful in project.el, see
> `project-kill-buffer-conditions'.  In that case you want to both be able
> to say something like "kill buffers only if they are in
> fundamental-mode", but also something like "kill all buffers that are
> based on comint-mode".

So this is only because of fundamental-mode?  If so, shouldn't it be
enough to have a possibility to have a predicate function, which can
do anything one likes?

I think we want in general avoid comparison with major-mode, and
prefer derived-mode instead, and if so, IMO we had better did as we
say and not exposed comparison to major mode unless we absolutely
must.