====header tag====

It is often very useful to want to reuse a certain set of macro calls in every passage,
or to reuse an opening block of text. You can do this by giving the passage the special
tag ''%%header%%'', or ''%%footer%%''. All passages with these tags will have their source text included at the top
(or, for ''%%footer%%'', the bottom) of every passage in the story, as if by an invisible [[harlowe:display|(display:)]] macro call.

If many passages have the ''%%header%%'' tag, they will all be displayed, ordered by their passage
name, sorted alphabetically, and by case (capitalised names appearing before lowercase names).