Merge branch 'js/rebase-in-c-5.5-work-with-rebase-i-in-c'

Merge branch 'js/rebase-in-c-5.5-work-with-rebase-i-in-c'

"rebase" that has been rewritten learns the new calling convention
used by "rebase -i" that was rewritten in C, tying the loose end
between two GSoC topics that stomped on each other's toes.

* js/rebase-in-c-5.5-work-with-rebase-i-in-c:
  builtin rebase: prepare for builtin rebase -i