tmac/tmac.an: define .MR in a groff compatible way

groff 1.23.0 added .MR to its -man macro package.  The NEWS file states
that the inclusion of the macro "was prompted by its introduction to
Plan 9 from User Space's troff in August 2020."  From d32deab it seems
that the name for Plan 9 from User Space's implementation was suggested
by groff maintainer G. Brandon Robinson.

Not sure if the intention was to make these definitions compatible, but
it would be nice if they were.

Currently, Plan 9 from User Space's .MR expects its second argument to
be parenthesized.  groff's .MR does not.  This results in extra
parentheses appearing in manual references when viewing Plan 9 from User
Space's manual pages on a system using groff.

1 files changed, 6 insertions, 6 deletions

diff --git a/man/man1/label.1 b/man/man1/label.1
index 6688972d..b1b481a1 100644
--- a/man/man1/label.1
+++ b/man/man1/label.1
@@ -14,12 +14,12 @@ label, awd \- set window label
 sets the label of the current 
 .I win
 (see
-.MR acme (1) )
+.MR acme 1 )
 or X terminal window
 .RI ( e.g.,
-.MR 9term (1)
+.MR 9term 1
 or
-.MR xterm (1) )
+.MR xterm 1 )
 by echoing a special control sequence to standard output.
 .PP
 .I Acme
@@ -38,7 +38,7 @@ sets the window name to the current directory with a
 suffix, using the name of the current system by default.
 .SH EXAMPLE
 One can use the following
-.MR sh (1)
+.MR sh 1
 function to keep the label up-to-date in response to
 .I cd
 commands:
@@ -55,7 +55,7 @@ alias cd=_cd
 cd .
 .EE
 .PP
-.MR Rc (1)
+.MR Rc 1
 installs a similar 
 .B fn
 .B cd
@@ -77,4 +77,4 @@ fn cd {
 .SH BUGS
 .I Awd
 is also documented in
-.MR acme (1) .
+.MR acme 1 .