[PATCH] emacs/tree: add notmuch-tree-filter

[William Casarin]

Tomi Ollila <tomi.ollila at iki.fi> writes:

> On Sat, Apr 25 2020, William Casarin wrote:
>
>> This implements the notmuch-tree version of notmuch-show-filter-thread
>> and binds it to the L key.
>
> No reasoning in commit message why 'L' is chosen...

oh right this should probably be `l`. I think I thought it was L because
evil rebinds notmuch-show-filter-thread from `l` to `L` and I didn't
realize this until now.