thread ordering based on references and/or in-reply-to

[Florian Friesdorf <flo@chaoflow.net>]

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Hi,

I'm looking into taking the References header into account for thread
ordering. So far only In-Reply-To is used. My C/C++ is rusty at best, so
I'd need some help to get this done.

Carl gave a try on irc already to clear things up for me, reading into
it, I have more questions:

lib/thread.cc/_resolve_thread_relationships adds messages as replies to
a parent.

Currently, we seem to treat In-Reply-To as empty or single msgid. If I
understand rfc822 it can be a list of msgids and/or phrases. Do/shall we
support that?

References is a list of msgids, with the last one being the direct
parent. I don't know how multiple direct parents are handled here.

DJB recommends "... readers look for identifiers in In-Reply-To and
append them to References if they are not already included in
References." [1]

In that case if there are two msgids in In-Reply-To and there are
appended to the References list, than only the last one will be a parent
and the one that used to be the last is not a parent anymore.

And Carl recommends to treat references and in-reply-to as two separated
sources of information, first using in-reply-to and then references in
order "to attach to the deepest referenced parent". 

I fail to understand that. Am I complicating things?
How do we want to treat the combination of References/In-Reply-To?

Do we have code that returns the last msgid listed in references?
database.cc/parse_references seems not to care about order, just
existence - or is GHashTable ordered.

[1] http://cr.yp.to/immhf/thread.html


florian
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Florian Friesdorf <flo@chaoflow.net>
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