bug#60929: 30.0.50; [FR] `file-name-extension' and backup suffixes

[Eli Zaretskii <eliz@gnu.org>]

> From: Ihor Radchenko <yantar92@posteo.net>
> Cc: 60929@debbugs.gnu.org
> Date: Wed, 25 Jan 2023 13:18:48 +0000
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >   . given "foo.org.~10~" return the list ("foo" org-mode backup)
> >   . given "foo.org.gpg.gz" return ("foo" org-mode epa-file compress)
> 
> I do not think that you can deterministically associate file extension
> with major mode. Alternative major modes do exist for some file
> extensions (like built-in python.el vs. python-mode.el). Just extension
> list may suffice in the simplest scenarios.

The intent was to use auto-mode-alist, of course.  Or are you saying
that you'd like, for example, to treat *.org files as Org files even
if the user customized auto-mode-alist to use a different mode?

> In addition, given "foo.txt.org.gpg.gz" may return
> ("foo.txt" "org" "gpg" "gz") not stripping the first .txt as it never
> affects how Emacs opens the file.

Talking about "opening the file" again narrows the scope of the
requested feature, IMO.  We don't want to assume that the application
would like to open the file.  Besides, Text mode does affect how Emacs
treats the file.