bug#11339: 24.1.50; read-{buffer,file-name}-completion-ignore-case fails on non-ascii

[Eli Zaretskii]

> From: Stephen Berman <stephen.berman@gmx.net>
> Cc: stefan@marxist.se,  11339@debbugs.gnu.org
> Date: Sat, 02 Nov 2019 16:09:31 +0100
> 
> Concerning my followup to my OP, that involved another difference I
> observed in completion behavior between buffer names and file names with
> non-ASCII characters when *-completion-ignore-case is non-nil, and
> that's what the recipe above shows in more detail than in my followup,
> which didn't explicitly contrast the behavior with ASCII-only characters
> (the above recipe also uses names that differ beyond the case
> differences, to avoid the question of expectations where only case
> differs): with buffer names, all completions are shown regardless of the
> case of the input, but with file names, completion is done according to
> the case of the input, i.e. read-file-name-completion-ignore-case
> appears to have no effect (again, only when the names contain non-ASCII
> characters).  This seems to be a clear bug.

Yes, it was a bug, and a very old one: our case-insensitive comparison
of file names worked by bytes, which is only TRT for pure-ASCII
strings.

I hope I fixed this now, please try the latest master.