bug#50431: revert-buffer doesn't preserve read-onlyness

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 50431@debbugs.gnu.org
> From: Juri Linkov <juri@linkov.net>
> Date: Thu, 25 Aug 2022 21:02:00 +0300
> 
> >> I confirm that now the read-only status is restored,
> >> but reverting loses view-mode:
> >>
> >>   C-h C-t  -- note "View" on the mode-line;
> >>   C-x x g  -- "View" is lost.
> >
> > Hm, yes.  Reverting a buffer disables all the minor modes?
> 
> Maybe minor modes should be restored after reverting?

Only the minor modes that are automatically turned on when visiting
the file.  Reverting should produce the same effect as killing the
buffer and then visiting the file anew, nothing more, nothing less.

For that reason, I'm not sure the change that preserves the read-only
status across reverts is correct.  At the very least, it should be an
opt-in feature, IMO.