set group id not taking effect?

[Paul Edwards]

My repository is under a particular unix group, say groupa.

I have a user who is not in groupa.

No problem, I just did a chmod g+s cvs

and asked them to try again.

Nope, it fails because $CVSROOT/CVSROOT is not writable.
Indeed, it is not world writable, but I expected the setgid to take
care of that.

Sun Solaris.
CVS 1.11.6

the executable is in a directory that is allowed to have setuid,
although I just realised I didn't specifically check if setgid was
allowed or not.  Certainly the bit was set, but I didn't think of
checking /etc/mnttab until just now.  Any ideas?

Thanks.  Paul.