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

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Cc: larsi@gnus.org,  50431@debbugs.gnu.org
> Date: Thu, 25 Aug 2022 22:35:31 +0300
> 
> >> 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.
> 
> In the above example, `C-h C-t' `C-x x g' doesn't preserve the same state
> as visiting the file anew with `C-h C-t'.
> 
> > 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.
> 
> It was a regression when reverting stopped to preserve the read-only status
> that worked in older versions.

IMO, that was a mistake.  It violates the notion of "reverting", at
least in my book.