bug#16133: 24.3; copy-file fails on chmod when copying to FAT filesystem

[Eli Zaretskii]

> From: Josh <josh@foxtail.org>
> Date: Sat, 14 Dec 2013 13:21:58 -0800
> Cc: Glenn Morris <rgm@gnu.org>, Paul Eggert <eggert@cs.ucla.edu>, 
>       Валерия Лихушина <ran@lasgalen.net>, 
>       16133@debbugs.gnu.org
> 
> >> It might be reasonable to error only when the existing
> >> PRESERVE-UID-GID argument was non-nil.
> >
> > That argument has nothing to do with mode bits, which is what this bug
> > is about.
> 
> That argument being nil indicates that the user doesn't care about
> preserving UID and GID.  Are there cases when the user would care
> about preserving mode bits but not UID and GID?

Definitely.  MS-Windows is one such case.