tests/test-rollback

Fix up parent display in logging

For changesets with a first parent nullid, but not rev 0, we ought to
display a null parent.

#!/bin/sh

mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m "test" -d "1000000 0"
hg verify
hg parents
hg status
hg rollback
hg verify
hg parents
hg status