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.
#require no-icasefs
test file addition with colliding case
$ hg init repo1
$ cd repo1
$ echo a > a
$ echo A > A
$ hg add a
$ hg st
A a
? A
$ hg add --config ui.portablefilenames=abort A
abort: possible case-folding collision for A
[255]
$ hg st
A a
? A
$ hg add A
warning: possible case-folding collision for A
$ hg st
A A
A a
$ hg forget A
$ hg st
A a
? A
$ hg add --config ui.portablefilenames=no A
$ hg st
A A
A a
$ mkdir b
$ touch b/c b/D
$ hg add b
adding b/D
adding b/c
$ touch b/d b/C
$ hg add b/C
warning: possible case-folding collision for b/C
$ hg add b/d
warning: possible case-folding collision for b/d
$ touch b/a1 b/a2
$ hg add b
adding b/a1
adding b/a2
$ touch b/A2 b/a1.1
$ hg add b/a1.1 b/A2
warning: possible case-folding collision for b/A2
$ touch b/f b/F
$ hg add b/f b/F
warning: possible case-folding collision for b/f
$ touch g G
$ hg add g G
warning: possible case-folding collision for g
$ mkdir h H
$ touch h/x H/x
$ hg add h/x H/x
warning: possible case-folding collision for h/x
$ touch h/s H/s
$ hg add h/s
$ hg add H/s
warning: possible case-folding collision for H/s
case changing rename must not warn or abort
$ echo c > c
$ hg ci -qAmx
$ hg mv c C
$ cd ..