bug#49893: [PATCH] Reset mtime of a reverted buffer

[Eli Zaretskii]

> From: Konstantin Kharlamov <hi-angel@yandex.ru>
> Cc: 49893@debbugs.gnu.org
> Date: Thu, 05 Aug 2021 19:54:03 +0300
> 
> On Thu, 2021-08-05 at 19:36 +0300, Eli Zaretskii wrote:
> > > From: Konstantin Kharlamov <hi-angel@yandex.ru>
> > > Date: Thu, 05 Aug 2021 18:28:28 +0300
> > > 
> > > Patch is attached. This resolves the problem reported at
> > > https://github.com/emacs-evil/evil/issues/1504
> > 
> > Could you please describe the problem you are trying to solve,
> > preferably without involving Evil?
> 
> Sure. The auto-revert-mode by default works with 
> ‘revert-buffer-insert-file-contents--default-function’ function. This 
> function is known to break markers in buffers, which is why recently Emacs 
> has added a replacement function 
> revert-buffer-insert-file-contents-delicately (the one I modify in the patch).
> 
> However, actually trying to use this new function revealed a regression in 
> behavior of another function: the `find-file`. Basically, if you have a file 
> `/tmp/foo` opened in Emacs (IOW Emacs has a buffer associated with this 
> file), and then file `/tmp/foo` gets "auto-reverted", then if you execute 
> (find-file "/tmp/foo"), the new function causes Emacs ask a user "File foo 
> was modified, do you want to revert it? (yes/no)". It now gives that prompt 
> always, until you make a change to the buffer.
> 
> That's a regression compared to the default behavior with 
> `revert-buffer-insert-file-contents--default-function`. And the reason turned 
> out to be that the function 
> `revert-buffer-insert-file-contents--default-function` after having 
> succesfully reverted a file, sets the buffer mtime to the mtime of the file. 
> However the function revert-buffer-insert-file-contents-delicately didn't set 
> mtime before that patch. I assume it is an omission from implementation, 
> because technically that's incorrect: if the 
> revert-buffer-insert-file-contents-delicately has successfully reverted a 
> buffer, then we know that it has same content as the associated file, and 
> hence it should have the same mtime.

Thanks.  I installed the change on the master branch.