bug#50658: Error messages including function names violates coding conventions

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Sat, 18 Sep 2021 04:58:01 -0700
> Cc: 50658@debbugs.gnu.org
> 
> >> 2. We modify the above coding convention to say that including the
> >>    function name at the start is okay.  Presumably this includes
> >>    updating checkdoc to check that it is actually the function name that
> >>    is used (or perhaps to just accept any symbol).
> >
> > I think 2 is TRT, except that it isn't really a change in the
> > conventions.
> 
> How about this clarification:
> 
> diff --git a/doc/lispref/tips.texi b/doc/lispref/tips.texi
> index a72ab88cef..c6c16211e4 100644
> --- a/doc/lispref/tips.texi
> +++ b/doc/lispref/tips.texi
> @@ -392,8 +392,9 @@ Programming Tips
>  @code{beep} to report errors.
> 
>  @item
> -An error message should start with a capital letter but should not end
> -with a period.
> +An error message should start with a capital letter or a Lisp symbol,
> +as in ``foo-command: Invalid input''.  It should not end with a
> +period.

Thanks.  If we are going to show examples (which is a good idea, IMO),
I think we should show both examples with and without the function
name, and therefore some wording about the function name being
optional, and that the rule is not applicable to it, is in order.