> From: Paul Eggert <eggert@cs.ucla.edu>
> Cc: Eli Zaretskii <eliz@gnu.org>, 27986@debbugs.gnu.org
> Date: Sun, 13 Aug 2017 16:48:59 -0700
>
> Getting back to Philipp's original bug report, Apple documentation says macOS
> has a facility like the Linux renameat2 system call (i.e., it's like 'renameat'
> except it can be told to fail if the destination already exists). Attached is a
> proposed patch to use this facility, which means that the case-insensitivity
> test would no longer need to be done in macOS. If there's some way to implement
> renameat_noreplace on MS-Windows we could get rid of the case-insensitivity test
> there too.

There's nothing easier than implementing renameat_noreplace on
MS-Windows, since the underlying system call does that by default, and
it's emulating the Posix behavior that requires complications.