bug#22300: 25.1.50; Dired -- renaming folders/files to CamelCase/UPPERCASE/lowercase.

[Eli Zaretskii]

> Date:  Sun, 03 Jan 2016 20:19:50 -0800
> From:  Keith David Bershatsky <esq@lawlist.com>
> Cc:  22300@debbugs.gnu.org,Drew Adams <drew.adams@oracle.com>,John Wiegley 
> <jwiegley@gmail.com>
> 
>   (let ((default-directory "/Users/HOME/Desktop/"))
>     (rename-file "/Users/HOME/Desktop/FOO" "/Users/HOME/Desktop/foo" 
> 'ok-if-already-exists))
> 
> which yields the following debugger output:
> 
>   (file-error "Renaming" "Invalid argument" "/Users/HOME/Desktop/FOO" 
> "/Users/HOME/Desktop/foo/FOO")

This is expected, if your filesystem is case-insensitive.  See my
other messages for the explanation why.

The question is: are all OS X filesystems case-insensitive.  If they
are, we just need to reuse the DOS_NT code that's already in
rename-file.