testing for a valid tag name in bash

[Kenneth Dombrowski]

Hi,

I'm writing some bash scripts to ease the management of a website for a
group of people not necessarily well-versed in cvs.  The workflow goes
from a checked out version of the HEAD branch to an exported test/QA
site, and finally to an exported live site.  The update script for the
dev site was easy since it's always the HEAD anyway, but for the others
I want to enforce tag names be used.  My 'exporttest' script works fine
given a valid tag, but currently just exits happily when given a bogus
tag.  It seems that given a nonexistent tag, provided cvs itself doesn't
die, `cvs export` always returns true, though it outputs a message on
STDERR.

Is there a reliable way to query cvs whether a given tag exists?  

Thanks!
Kenneth