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

[Eli Zaretskii]

> From: Stephen Leake <stephen_leake@stephe-leake.org>
> Date: Wed, 04 Nov 2015 03:04:41 -0600
> Cc: Juanma Barranquero <lekktu@gmail.com>, 21816@debbugs.gnu.org,
>       Dmitry Gutov <dgutov@yandex.ru>
> 
> Windows 8.1 lets me create:
> 
> "c:/tmp/STRAẞE.text" ;; LATIN CAPITAL LETTER SHARP S
> "c:/tmp/Straße.text" ;; LATIN SMALL LETTER SHARP S
> "c:/tmp/Strasse.text"

Windows is right: ẞ is not the upper-case variant of ß.  See
UnicodeData.txt and SpecialCasing.txt.

> Perhaps Windows has simply not yet implemented this recent addition to
> Unicode?

It's not recent: it appeared in Unicode 5.1, 7 years ago.

> Debian testing (a few months old) running in VMWare under Windows 8.1
> shows the same behavior. But Debian is case-sensitive, so that's not an
> issue here, I think. The upcase/downcase is wrong, but I'm guessing
> that's due to the CAPITAL being a recent addition to Unicode. 

No, it's because Unicode doesn't say these two letters are a case
pair, at least not in the usual sense.