-If the third parameter is passed and is true, an absolute url will be
-constructed instead of the default relative url.
+If the second parameter is not specified (or `undef`), the URL will be
+valid from any page on the wiki, or from the CGI; if possible it'll
+be a path starting with `/`, but an absolute URL will be used if
+the wiki and the CGI are on different domains.
+
+If the third parameter is passed and is true, the url will be a fully
+absolute url. This is useful when generating an url to publish elsewhere.