Re: the compatibility of man(7) (was: man(7) .TH font change, was: groff man(7) `B` macro...)

[Ingo Schwarze]

Hi Alejandro,

Alejandro Colomar wrote on Mon, Aug 01, 2022 at 03:47:19PM +0200:

> Maybe adding "(since groff 1.23.0)" next to the description of MR in the 
> groff manual should be enough to trigger some doubts in programmers.

Putting compatibility information and in particular version numbers
in the middle of the DESCRIPTION is slightly unusual, but in a drastic
case like this, it might actually help to alert authors to situations
where using the new feature is premature.
If all goes well and the new feature is taken up by most systems
after a number of years, we should not forget to relegate it to the
HISTORY section it will then belong, in order to avoid littering the
main text of the description.

[...]
> Checking which versions of a program are packaged for different 
> distros/OSes should be trivial in most cases.

True, for example with repology.org and similar sites.
So "since" together with the groff version number does sound helpful.

[...]
> I think the think that will save us is that people usually don't even 
> know that groff exists or that it's used internally by man(1) to render 
> the pages.  So, programmers are unlikely to run `man groff_man`, and 
> instead will go for `man 7 man`, which will not talk about MR.

Oh, the man(7) from the man-pages package.  That's probably
another partial mitigation, yes.

The man(7) shipped with mandoc(1) will mention .MR once it is
implemented there, but not in the MACRO OVERVIEW and only in
the MACRO REFERENCE, similar to the other GNU extensions
like .UR and .TQ, marking it as a Plan9+GNU extension,
probably also mentioning "since groff 1.23.0" as you suggest.

Yours,
  Ingo