Re: Rmail: new feature to deal with In-Reply-To and References headers

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 09 Dec 2023 21:54:36 +0000
> From: rameiko87@posteo.net
> Cc: emacs-devel@gnu.org
> 
> > AFAIU, you should already be able to do that in Emacs 29, by using the 
> > new command rmail-summary-by-thread.  After creating that summary, you 
> > can use the usual message movement commands to move between messages 
> > belonging to a thread.
> 
> In fact it's not the case, because the order on the summary buffer 
> centered on a given message does not correspond in general to the 
> parents-descendants order of the thread containing that given message, 
> as defined by moving up on the References header for that message.
> 
> >> Move to the previous message in the same thread as the current one 
> >> (that is, the message whose Message-ID is the last entry of the 
> >> References header, among messages in the Rmail file). Repeat argument 
> >> goes back to the n-th last entry of the References header among 
> >> messages in the Rmail file.
> 
> This feature is not implemented currently unless the parents vector is 
> populated with the same order given by the References header. Someone 
> remembers how the parents vector is recursively defined in rmailsum.el?
> 
> And still, going up on the chain requires regenerating the summary 
> buffer by centering every time on the parent.
> 
> >> Move to the message which the current message is replying to (that is, 
> >> the message whose Message-ID appears in the In-Reply-To header), error 
> >> if not present on the Rmail file. Repeat argument iterates the command 
> >> n-times, perhaps replacing the messages which it can't find in the 
> >> Rmail file by their youngest parent.
> 
> This is not implemented currently.

Patches to improve the existing implementation of by-thread summary
will be welcome, of course.  It is a new feature, so I'm not surprised
that it has some rough edges.

Adding Andrea, who implemented this feature, in the hope that he will
have some comments or maybe patches.