wish list: thread-gathering sort options

[Ken Raeburn <raeburn@raeburn.org>]

I'm trying to change the way my mail groups are sorted.  I've been
gathering threads by subject, and sorting by date.  What I'd like to
do instead is sort by "last date the thread way active".  Finding and
sorting on the latest date in a thread isn't hard, I wrote that code.
Problem is, the thread gathering assumes that when threads are
gathered, they should go in the position of the first thread, and the
sorting is applied before gathering threads.  In my case, the latest
thread is the last one, and that's the position where I want the
gathered threads to go.

I could probably get something more consistent to happen by putting
newest threads first, but I want the current (oldest-first) style of
listing both for sorting gathered threads and for the separate threads
gathered together.  I just want to use the latest date in the gathered
threads as the sort key.

Can I have some sort of option to control how gathered threads are
placed, or perhaps sort after gathering?

Ken