(emacs) :sort-order 'oldest-first ignored with :search-type 'tree

[Leo Gaspard]

Hello!

I've recently (hear: yesterday) switched to emacs' notmuch-mode for mail
handling. So first, thank you for the work you are doing with notmuch,
it's really great!

Now, time for the less-fun stuff: things that were not perfect during
the migration. There weren't many (and the advantages largely outweigh
the issues!) but as well tell them. So here it goes, spread over this
mail and the two following ones.

I'm not sure which versions are of interest here, but I'm with
notmuch 0.27 and emacs 26.1.

For this email, it looks like a search filter with
    :search-type 'tree
will ignore any :sort-order argument defined.

This is unexpected, and I'd have loved being able to see messages
threaded and in oldest-to-newest order.

Thank you for notmuch!
Cheers,
Leo