.Xr mdoc(7) from groff_mdoc(7)?

[Ingo Schwarze]

Hi,

given that two authoritative manual pages for the mdoc language
exist that describe exactly the same language, but in a somewhat
different style, an anonymous coward calling himself "B 9" just
suggested in passing in a remark in a bugtracking ticket that it
might occasionally help users if both authoritative pages would
reference each other.  So i went ahead and added this sentence to
the SEE ALSO section of the mdoc(7) manual page in the mandoc
distribution:

  The manual page groff_mdoc(7): https://man.voidlinux.org/groff_mdoc
  contained in the "groff" package documents exactly the same language
  in a somehwat different style.

Are GNU troff developers OK with adding the reverse link to
the SEE ALSO section of the groff_mdoc(7) manual page, as in
the patch below?

Of course, i'm open to tweaks of the wording.

The point in not using .Xr in such an unusual case is two-fold: on
the one hand, people having installed groff do not necessarily have
mandoc installed and vice versa, so an .Xr can easily result in
dead links.  On the other hand, the bare manual page name mdoc(7)
without an URI could lead people to the wrong manual page, the
ancient mdoc(7) page that became obsolete twenty years ago but
unfortunately still floats in various places on the web.

This patch seemed too minor to open a ticket, i thought feedback is
likely to be quicker and simpler with just a straightforward email.

OK?
  Ingo

P.S.
Regarding the link in the mandoc mdoc(7) page, i would have preferred
an authoritative URI below https://www.gnu.org/ but couldn't find any.
Void Linux is generally very well maintained and very up-to-date,
so i see no risk that the link dies next year.  Debian would of
course work, too, but the URI
  https://manpages.debian.org/unstable/mandoc/mandoc_mdoc.7.en.html
unfortunately feels excessively ugly...


diff --git a/tmac/groff_mdoc.7.man b/tmac/groff_mdoc.7.man
index 6aec5a11..03f06395 100644
--- a/tmac/groff_mdoc.7.man
+++ b/tmac/groff_mdoc.7.man
@@ -4245,6 +4245,12 @@ Multiple man pages (in either format) can be handled.
 .Xr man 1 ,
 .Xr troff 1 ,
 .Xr groff_man 7
+.Pp
+The manual page
+.Lk https://man.openbsd.org/mdoc.7 "mdoc(7)"
+contained in the
+.Dq mandoc
+package documents exactly the same language in a somehwat different style.
 .
 .
 .Sh BUGS