Speedup revlog.ancestors for the linear case revlog.ancestors can be expensive on big repos. This cuts down the overall time for hg update by ~19% by short cutting revlog.ancestors when one of the revisions is reachable from another.

#!/bin/sh

hg init
mkfifo p

hg serve --stdio < p &
P=$!
(echo lock; echo addchangegroup; sleep 5) > p &
Q=$!
sleep 1
kill -HUP $P
sleep 1
ls .hg