bug#65719: [PATCH] Pass restart argument to 'kill-emacs-query-functions'

[Stefan Kangas <stefankangas@gmail.com>]

me--- via "Bug reports for GNU Emacs, the Swiss army knife of text
editors" <bug-gnu-emacs@gnu.org> writes:

> Small change here to pass the restart status to
> 'kill-emacs-query-functions' in 'save-buffers-kill-emacs' so any
> functions there can react to being restarted, sample use-case this may
> be useful is if one is using a package like perspective.el to handle
> buffer/window management and when calling `M-x restart-emacs` you WANT
> your last session to be persisted, but just starting Emacs normally you
> don't.
>
> There are other potential use-cases for this too, so hopefully this
> patch is well-received.

Thanks.  The feature sounds useful, and the use-case makes sense.  But
isn't the change backwards-incompatible?  Can we find a way to do this
without any breaking changes?

One idea would be to simply introduce a new variable that takes the
argument, while making the old one obsolete.  That would allow people to
slowly migrate over to the new one, without everything suddenly breaking
under their feet.