bug#23033: 24.5; Lock file uses the same extension as the file it's locking

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Sun, 26 Sep 2021 00:17:24 -0700
> Cc: Eli Zaretskii <eliz@gnu.org>, rgm@gnu.org, 23033@debbugs.gnu.org, 
> mgsloan@gmail.com
> 
> > Perhaps they're combined auto-save and lock files?
> 
> Something like that would be my guess.  The name ".swp" suggests it's
> got more to do with auto-saving.
> 
> But come to think of it, would it be possible for us to use one combined
> file?

That'd complicate Emacs in non-trivial ways.  Currently, the auto-save
file is just a snapshot of the file's buffer, and the lock file is a
specialized file whose content tells us who and when locked it.  To
put both of these in the same file would mean the file will need
parsing.  Does it really make sense to do that?