bug#13125: Fix permissions bugs with setgid directories etc.

[Chong Yidong]

Paul Eggert <eggert@cs.ucla.edu> writes:

> I'm attaching a patch, which changes file-attributes so that it now
> outputs a placeholder value instead of the old 9th attribute member,
> since the value is rarely needed and almost nobody seems to be using
                     ^^^^^^

Have you actually done a survey of all the callers to file-attributes to
see if this is true?

> Instead, the patch moves this functionality to
> file-ownership-preserved-p via a new argument GROUP.

Why can't this functionality be kept in file-attributes?