rebase: fix rebase with no common ancestors (
issue4446)
The new rebase revset didn't check for the case when there are no common
ancestors. Now it does. The new behavior should be the same as the pre-3.2
behavior. Added a test.
$ hg init
$ touch unknown
$ touch a
$ hg add a
$ hg ci -m "1"
$ touch b
$ hg add b
$ hg ci -m "2"
Should show unknown
$ hg status
? unknown
$ hg revert -r 0 --all
removing b
Should show unknown and b removed
$ hg status
R b
? unknown
Should show a and unknown
$ ls
a
unknown