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

[Tino Calancha]

On Thu, 29 Apr 2021, Eli Zaretskii wrote:

> > > (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.
OK.  It makes a lot of sense.