Thanks, but I don't think that this is a portable grep pattern:
$ echo "abc" | grep '\(a\|x\)'
$ echo "abc" | egrep '(a|x)'
abc
But then, this is on some AIX 4.3. How about:
fgrep -e "refs/heads/$ref" -e "refs/tags/$ref"
or
grep -e "^refs/heads/$ref" -e "^refs/tags/$ref"
-- Hannes