bug#18336: 24.4.50; When editing externally changed file, Emacs asks too many questions

[Eli Zaretskii]

> From: Noam Postavsky <npostavs@gmail.com>
> Cc: dak@gnu.org,  stefan@marxist.se,  18336@debbugs.gnu.org
> Date: Sat, 21 Mar 2020 21:13:59 -0400
> 
> >> Why exactly are we calling lock_file from write_region?
> >
> > Because write-region can be called from an unmodified buffer, I
> > suppose, and from a buffer whose buffer-file-name is not the same as
> > the file being written to.
> 
> So maybe we could just check those conditions?  Here's a patch,
> tentatively suggested for master.

Isn't it better to check whether the file is already locked?  That
way, we don't need any (error-prone) heuristics for when it's okay to
ask the question and when it isn't.

> > Evidently, when we disabled backups in /tmp, we missed the fact that
> > lock_file called from write-region will be affected.  When backups are
> > not disabled, this works correctly.
> 
> To me, the fact that it works with backups enabled seems like an
> accident.

It might be an accident, but it's the reason why the default paradigm
works.

Thanks.