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

[Paul Eggert]

I couldn't reproduce the problem on my Ubuntu system
(Ubuntu 13.10); when I copied a file to a FAT file system
there was no diagnostic.

I don't understand what is meant by
"FAT filesystem with file permissions 0075".
I tried to create a directory with those permissions,
using "mkdir dir; chmod 0075 dir", but as far as Ubuntu
was concerned the chmod had no effect (it claimed to be
successful, but it didn't change the directory permissions).
Similarly, when Emacs copy-file runs, chmod has no effect
but returns 0 so Emacs thinks the chmod worked and does
not throw an error.

Perhaps there's something unusual about how your file system
was mounted?  If so, it'd help to know more about it in
order to reproduce the problem.