bug#46374: 28.0.50; Ask me to save buffers only if they are under callers dir

[Eli Zaretskii]

> From: Tino Calancha <tino.calancha@gmail.com>
> Date: Wed, 28 Apr 2021 22:35:02 +0200
> Cc: 46374@debbugs.gnu.org, Stefan Monnier <monnier@iro.umontreal.ca>,
>  Quách Mỹ Uyên Nhi
>  <uyennhi.qm@gmail.com>
> 
> Juri Linkov <juri@linkov.net> writes:
> 
> > (defun save-some-buffers-fun ()
> >   (funcall save-some-buffers-default-predicate))
> >
> > I see a problem in save-some-buffers-fun: what if
> > save-some-buffers-default-predicate is still customized to nil?
> I assumed we were OK with the backward incompatible change; I mean,
> with requiring from now on `save-some-buffers-default-predicate'
> to be a function generating the predicate.

No, we always prefer backward-compatible changes where it is
practical.