bug#50840: 28.0.50; Support GNU style of multiline comments in C source code

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 27 Sep 2021 18:35:50 +0000
> Cc: 50840@debbugs.gnu.org, Stefan Monnier <monnier@iro.umontreal.ca>,
>   acm@muc.de
> From: Alan Mackenzie <acm@muc.de>
> 
> > Is this true?  If so, a feature request: add a style to support that.
> > If such a style already exists, please clarify the documentation so that
> > users could understand which style does that.
> 
> > And one more nit: Can the 'comment-end' inserted after the end of a
> > comment please keep _two_ spaces after the period that ends the last
> > line of a comment?  Or at least heed the setting of
> > 'sentence-end-double-space'?
> 
> Are we talking about C-c C-c (aka M-x comment-region) here?

Yes, my use case, and the context in which I filed the bug report, was
"C-c C-c".  Not only for the 2 spaces issue, but also for the comment
style.

> This command currently inserts comment-end (in C Mode, " */") at the
> end of each line being commented, which will leave a single space
> between what was the last "." on the line and the "*/".
> 
> We could surely check for an end of sentence character at EOL here, and
> if we've got one, check that at least two spaces are left.  This again
> would be something for lisp/newcomment.el.

Probably.  That''s why Stefan was CC'ed as well.