bug#13329: 24.2 post patch for #9521; Rmail forward does not correctly handle MIME messages containing "From " lines

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Eli Zaretskii <eliz@gnu.org>,  13329@debbugs.gnu.org
> Date: Thu, 09 Jun 2022 19:18:55 +0200
> 
> Lars Ingebrigtsen <larsi@gnus.org> writes:
> 
> >>     If you forward a Rmail message containing a MIME message with "From "
> >> lines, the mbox escaping of From lines is not properly done.
> >
> > (I'm going through old bug reports that unfortunately weren't resolved
> > at the time.)
> >
> > I don't use rmail much myself, but I vaguely recall that there was a
> > similar bug report about this, and that this had been fixed at some
> > point.
> >
> > Perhaps Eli remembers; added to the CCs.
> 
> This was a month ago -- Eli, do you remember?

I don't remember, sorry.  I also didn't see anything pertinent in the
Git logs.

Moreover, upon re-reading the original report several times, I don't
think I understand what exactly is the bug: the original report is a
multipart message which is hard to parse.  It also shows what I think
is a single message, but says "The result should be 3 messages", which
left me utterly confused.

I'd prefer to have a description with 2 attachments: the original
message, and the forwarded message.  And the description should tell
in full what was expected to be seen, and why, preferably without
using ellipsis and hard-to-understand terminology such as "under
mboxrd".

Is it possible to get such a detailed report?  Then I could try the
messages here and see if there's still a problem left in our current
sources.

At this point I can only say that I'm forwarding email with MIME
attachments quite a lot, and didn't spot any problems, although I
admit there's not a lot of ">>...>From" in them.