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