bug#48937: 13.0.12; Paragraph filling with line that ends in % followed by comment

[Gustavo Barros]

Hi Tassilo,

On Wed, 09 Jun 2021 at 16:05, Tassilo Horn <tsdh@gnu.org> wrote:

> Indeed, that's a corner case nobody has bothered to handle yet.  I've
> pushed a fix to master.  Please give it a try.
>
> If you don't have a git checkout handy, you can also `eval-defun' the
> function below containing the fix.

Thank you very much for the quick answer and fix.

I did try it out, and I admit that that regexp is a little daunting to 
me.  But I was particularly not understanding why the "[^\r\n\\]" before 
`TeX-comment-start-regexp' in the patch. I still don't get its intent 
well, but I could get it to fail again by a small adjustment of the ECM, 
namely by removing the space between the `\%' and the comment character, 
so that we have `\%%'. This case fails to match because "[^\r\n\\]" must 
include one character before `TeX-comment-start-regexp'.

#+begin_src latex
\documentclass{article}

\begin{document}

Lorem ipsum dolor sit amet, consectetuer adipiscing elit.  Ut purus
elit, vestibulum ut, placerat ac, adipiscing vitae, felis.  Curabitur
dictum gravida mauris.  Nam arcu libero, nonummy eget, consectetuer
id, vulputate a, magna.  Donec vehicula augue eu neque.  Pellentesque
habitant morbi tristique senectus et netus et malesuada fames ac
turpis egestas. 35\%% FIXME check this number
Mauris ut leo.  Cras viverra metus rhoncus sem.  Nulla et lectus
vestibulum urna fringilla ultrices.

\end{document}
#+end_src

Bye,
Gustavo.