bug#57266: Maintaining the base_line_number cache

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: 57266@debbugs.gnu.org
> Date: Mon, 22 Aug 2022 08:41:41 -0400
> 
> > I didn't just mean just_this_one_p thingy, I meant all the changes
> > that attempt to somehow "clean up" the use of the line-number cache.
> > Why do we have to do that at all?  This stuff is not too complex, and
> > it works for ages!  Isn't the fact that we find more and more small
> > issues with the changes telling you something?
> 
> Yes, it's telling me that the code is a mess and I'm trying to fix it by
> documenting what is actually needed.

It's fine to fix and enhance the documentation, but please don't fix
the code that works.