* token to explain the kind of argument this option wants. Does not
* begin in capital letter, and does not end with a full stop.
* Should be wrapped by N_() for translation.
+ * Is automatically enclosed in brackets when printed, unless it
+ * contains any of the following characters: ()<>[]|
+ * E.g. "name" is shown as "<name>" to indicate that a name value
+ * needs to be supplied, not the literal string "name", but
+ * "<start>,<end>" and "(this|that)" are printed verbatim.
*
* `help`::
* the short help associated to what the option does.