bug#46397: 27.1; Cannot delete buffer pointing to a file in a path that includes a file

[Eli Zaretskii]

> From: Matt Armstrong <matt@rfc20.org>
> Cc: 46397@debbugs.gnu.org, eggert@cs.ucla.edu, craven@gmx.net
> Date: Wed, 24 Feb 2021 09:37:49 -0800
> 
> I still like my original idea of calling display-warning for all unlock
> errors, essentially turning "unlock" into a best effort function at the
> API level.  I think display-warning is intrusive enough that users are
> unlikely to simply not notice the problem, and there are worse things
> than leaving lock files around.

OK, you've convinced me: let's try the warning approach.  Can you
present a patch for that, please?

As for the tests you posted: too many of them rely on Posix file
modes, and thus will probably either fail or be unable to provide
meaningful testing on MS-Windows.  Can we please augment that by tests
that create unlocking problems by, e.g., running a shell command to
remove or rename or otherwise sabotage the lock file, so that the new
functionality could be meaningfully tested on Windows as well?