bug#30823: 25.3; modification-hooks of overlays are not run in some cases

[Eli Zaretskii]

> From: Noam Postavsky <npostavs@gmail.com>
> Cc: victorhge@gmail.com,  30823@debbugs.gnu.org,  monnier@iro.umontreal.ca
> Date: Thu, 23 Aug 2018 08:13:59 -0400
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Btw, I'm somewhat worried by the solution being proposed: it removes a
> > general safety device and replaces it by a solution that targets only
> > bug#21824, a much narrower class of problems.  Is that wise?
> 
> IMO, a safety device which causes new bugs is disqualified from its job.

I'm not sure it caused a new bug.

I'm hard pressed for free time lately, so I'd be grateful if you could
see whether it would be possible to make the original change smarter,
so that it avoids causing the current issue.  If not, I will try to
look into it in a couple of weeks or so.

> Furthermore, we're currently calling the after change hooks without
> the before change hooks which is just asking for trouble (as
> exemplified by Bug#21824 and this one).

That's a separate issue, isn't it?  We could refrain from calling the
after-change hooks as well.