Re: [GSoC][PATCH v4 2/2] rebase--interactive: rewrite append_todo_help() in C

> This rewrites append_todo_help() from shell to C. It also incorporates
> some parts of initiate_action() and complete_action() that also write
> help texts to the todo file.
> 
> This also introduces the source file rebase-interactive.c. This file
> will contain functions necessary for interactive rebase that are too
> specific for the sequencer, and is part of libgit.a.
> 
> Two flags are added to rebase--helper.c: one to call
> append_todo_help() (`--append-todo-help`), and another one to tell
> append_todo_help() to write the help text suited for the edit-todo
> mode (`--write-edit-todo`).
> 
> Finally, append_todo_help() is removed from git-rebase--interactive.sh
> to use `rebase--helper --append-todo-help` instead.