bug#21816: elisp-mode-tests fails on a case-preserving filesystem

[Eli Zaretskii]

> From: Stephen Leake <stephen_leake@stephe-leake.org>
> Cc: Juanma Barranquero <lekktu@gmail.com>,  Eli Zaretskii <eliz@gnu.org>,  
> 21816@debbugs.gnu.org
> Date: Tue, 03 Nov 2015 13:54:21 -0600
> 
>    If the file name identifies an existing file, convert the file name
>    casing to match the actual file name casing. If not, no case
>    conversion is done.

For existing files we have file-equal-p, which is more general.  The
problem here is that files might not exist, so we need a weaker test
that still does a reasonably good job.

> I'm not clear how to do the case conversion, but I bet Emacs does have
> the right functions.

It does.  Actually, we have more than one such function.

> This does not handle comparing two file names for a not-yet-created file
> that differ in case.

Indeed.