+.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.