del transaction before lock before wlock This way rollbacks happen while the repo is still locked. Deleting lock before wlock is not strictly necessary, but is more consistent with the locking order.

#!/bin/sh
# http://www.selenic.com/mercurial/bts/issue433

hg init a
cd a
echo a > a
hg commit -Ama

hg parents -r 0 doesnotexist
true