backout: allow backout of merge changeset with --parent option.
--parent allows to choose which parent of merge to revert to.
#!/bin/sh
hg init
touch unknown
touch a
hg add a
hg ci -m "1" -d "1000000 0"
touch b
hg add b
hg ci -m "2" -d "1000000 0"
echo %% Should show unknown
hg status
hg revert -r 0
echo %% Should show unknown and b removed
hg status
echo %% Should show a and unknown
ls