rebase: use "rebase.collapse" as "editform" for "--collapse" always
Before this patch, if both "--message" and "--collapse" are specified
for "hg rebase", "rebaes.normal" is used as "editform" unexpectedly.
Unlike patches before and after in this series for improvement, this
is bug fix patch.
Ancestors of 5
4 2 0
Ancestors of 6 and 5
3 4 2 1 0
Ancestors of 5 and 4
4 2 0
Ancestors of 7, stop at 6
6
Ancestors of 7, including revs
7 6 5 3 4 2 1 0
Ancestors of 7, 5 and 3, including revs
7 5 3 6 4 2 1 0
Descendants of 5
7 8
Descendants of 5 and 3
6 7 8
Descendants of 5 and 4
5 7 8