case "$THIS_SUB_DEPENDS" in
  VOLUME_ID) if ! list_find "$_EXTRAS_TARG" "extras/volume_id"; then
               message "Sub-dependency VOLUME_ID requested, adding build target 'extras/volume_id'." &&
               _EXTRAS_TARG="$_EXTRAS_TARG extras/volume_id" &&
               persistent_add _EXTRAS_TARG
             fi;;
          *) message "${PROBLEM_COLOR}bogus sub_depends: $SPELL $THIS_SUB_DEPENDS${DEFAULT_COLOR}"; return 1;;
esac
