djcb/mu — pull request #330 by xaiki (2013-12-21 18:44:36+00:00)
Title: Foldable threads in header view

The implementation is pretty silly:

+ put a marker everytime we come across a message that has a
'thread-level' of 0.
+ look for that marker, the line that has it is the thread header,
create an overlay for it.
+ the thread header is given different faces depending of it's folded
state
+ all lines after that marker up to another marker or end-of-file are
the subthreads, they are given another overlay.
+ the subthreads block overlay is given a face to customize it's look.
+ we only set-up overlays on demand (after rendering) so that we don't
slow header-view rendering.
+ as a bonus track, a function to recurse all thread groups is provided.

Signed-off-by: Niv Sardi