Use the pattern:
$PRETTY_NAME [$COMMIT_VERSION] (ostree[:$OSNAME][:$DEPLOYMENT_INDEX])
$OSNAME is only shown if there are multiple values.
$COMMIT_VERSION refers to the version tag in the commit's metadata.
$DEPLOYMENT_INDEX is only shown if no $COMMIT_VERSION is available.
https://bugzilla.gnome.org/show_bug.cgi?id=739416