Re: bsd group semantics

[Jeff King <peff@peff.net>]

On Tue, Mar 31, 2009 at 08:55:00AM -0700, Junio C Hamano wrote:

> IIRC, DIR_HAS_BSD_GROUP_SEMANTICS means you do not have to ask explicitly
> with g+s to the filesystem to use the "subdirectory is owned by the same
> group as its parent" semantics.  On SysV you have to ask; on BSD you do
> not have to (and do not need FORCE_DIR_SET_GID).

OK, I see. Thanks for the explanation. So the test is wrong, since it
explicitly checks for g+s, and we only need it sometimes.

> That one was not about "you do not have to ask", but "you are not allowed
> to ask because the request will fail".  Perhaps between FBSD4 and FBSD6
> things changed, and you can now make g+s request (which I presume is still
> a no-op other than setting the bit on)?

Yes, you can ask just fine now:

  $ uname -sr
  FreeBSD 6.1-RELEASE-p17-jc1
  $ mkdir foo
  $ ls -ld foo
  drwxr-xr-x  2 peff  peff  512 Mar 31 09:04 foo/
  $ chmod g+s foo
  $ ls -ld foo
  drwxr-sr-x  2 peff  peff  512 Mar 31 09:04 foo/

But it isn't necessary.

> Ideally the test should be checking if the subdirectory is owned by the
> same group as the toplevel, but that is rather hard to correctly arrange,
> as it depends on the set of groups the user who runs the test belongs to,
> how the git work tree is set up (if it is owned by his primary group or a
> secondary), etc.

Shouldn't that just be:

  perl -e 'sub group { return (stat(shift))[5] }' \
       -e 'exit group($ARGV[0]) == group($ARGV[1]) ? 0 : 1' \
       a b

?

-Peff