-.It Fl o Ns Ar base=http://base/
-The URL
-.Ar http://base/
-is used as a base URL for all relative links. This is useful when
-linking between documents via the
+.It Fl o Ns Ar includes=fmt
+The string
+.Ar fmt ,
+for example,
+.Ar ../src/%I.html ,
+is used as a template for linked header files (usually via the
+.Sq \&In
+macro). Instances of
+.Sq %I
+are replaced with the include filename. The default is not to present a
+hyperlink.
+.It Fl o Ns Ar man=fmt
+The string
+.Ar fmt ,
+for example,
+.Ar ../html%S/%N.%S.html ,
+is used as a template for linked manuals (usually via the