[Groff] mdoc: handle OpenBSD-style $Mdocdate CVS keyword

[Ingo Schwarze]

Hi,

in OpenBSD, we are using CVS keyword substitution to automatically
update the manual page date when committing to the manual page -
updating the date was too often forgotten before this was implemented,
and typos crept into the dates as well.  It looks like this:

.Dd $Mdocdate: March 5 2011 $
.Dt CAT 1
.Os

To make groff handle that, i'm using the following patch.

Maybe you want to include it upstream?
It costs very little, and it helps people who want to read
OpenBSD manuals on other operating systems.

Thanks,
  Ingo


--- tmac/doc-common.orig        Fri Dec 31 08:33:09 2010
+++ tmac/doc-common     Sun Oct 30 23:21:38 2011
@@ -685,7 +685,9 @@
 .  ds doc-command-name
 .
 .  ie \n[.$] \{\
-.    ie (\n[.$] == 3) \
+.    ie "\$1"$Mdocdate:" \
+.      ds doc-date-string \$2\~\$3, \$4
+.    el .ie (\n[.$] == 3) \
 .      ds doc-date-string \$1\~\$2 \$3
 .    el \{\
 .      ds doc-date-string "\*[doc-date-\n[mo]]