bug#74132: 31.0.50; thing-at-pt, ffap and Github markdown

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: enometh@meer.net,  74132@debbugs.gnu.org
> Date: Sat, 09 Nov 2024 11:59:44 -0500
> 
> >> > What will this do to URLs such as
> >> >   http://web.archive.org/web/20240221082647/https://www.imdb.com/
> >> Depends where point is: if it's after the `https`, then you get the
> >> "sub-URL" and if it's on or before the `https` then you get the whole URL.
> > Exactly.  This could be considered a bug, because the actual URL is
> > the entire thing.
> 
> We could refine our heuristic to as to keep looking backward when the
> apparent beginning of the URL is immediately preceded by a /, of course,
> but I'm not sure it's worth the trouble.

The problem is that AFAIU '/' is not the only such character.  It
could also be '=', I think (as in query URLs), and perhaps some
others.

> AFAICT any behavior we come up with will have such cases.

Yes, which is why I said I didn't know how to solve this.

> The [...](...) case mentioned by Madhu is a fairly common one IME, so
> I'm in favor of fixing it.

Not universally so, IME.  It is common in Markdown files and perhaps
also in Org.  So maybe this should be fine-tuned by major modes?