ticket notifications do not thread properly in mail clients

[raj@…]

The built in Trac notification system adds the References: header to ticket notifications that references the first email when the ticket was created which allows mail clients to properly thread the messages.

The Announcer emails do not have the References: header.

[Patrick Schaaf]

In the 0.11 version of AnnouncerPlugin there is an In-Reply-To and References header, but it is deficient, as it is simply set the same as the Message-ID on each message.

The essential feature of In-Reply-To / References headers is that they are the same over all messages belonging to the same ticket (or wiki page).

I'll append a patch which implements that in the 0.11 branch, which I currently use under trac 0.11.7; with these modifications my iPad email reader threads correctly.

Once I get around to testing trunk under 0.12 (gives me errors under 0.11.7...) I'll make a patch for trunk, too.

[Patrick Schaaf]

make In-Reply-To / References the same for the same ticket / wiki page

[Steffen Hoffmann]

Developer hint: Code went into announcer.email_decorators.ThreadingEmailDecorator, so it's enabled/disabled by enabling/disabling the component - a rather delicate choice, because we don't have a nice admin web-UI yet.

#9616 seems related.

[Steffen Hoffmann]

(In [12344]) TracAnnouncer: Improve efficiency of some email message headers, closes #8310.

Modified versions of the original patch fix some shortcoming of older announcer versions, especially regarding In-Reply-To / References headers, and Python doc-strings are corrected as well.

Thanks to bof for investigations on the issue, and even more for providing good suggestions by means of a working patch.