Merge branch 'aw/rebase-i-edit-todo'

Teach an option to edit the insn sheet to "git rebase -i".

* aw/rebase-i-edit-todo:
rebase -i: suggest using --edit-todo to fix an unknown instruction
rebase -i: Add tests for "--edit-todo"
rebase -i: Teach "--edit-todo" action
rebase -i: Refactor help messages for todo file
rebase usage: subcommands can not be combined with -i

diff --cc git-rebase--interactive.sh
Simple merge

diff --cc t/t3404-rebase-interactive.sh
Simple merge