Shell recipe for validating git tags

DOMAIN=com.example    # pre-sanitized
POLICY_FILE=policy-files/$DOMAIN.json
git pull
# retrieve all tags on commits that changed $POLICY_FILE 
# (with the additional constraint that at least one of the tags on each commit should be 
# named like example.com.2014.06.01.serial)
# the git log output looks like: (tag: tagname1, tag: tagname2, headname1, headname2)
TAGS=`git log --pretty=%d | egrep -o "[( ]tag: $DOMAIN[0-9\.]+" | cut -d":" -f 2`

for TAG in $TAGS ; do 
  if git tag --verify $TAG | check-for-correct-key-and-success ; then
    git show $TAG:$POLICY_FILE > current-valid-policy-file.json
    return $SUCCESS
  fi
done