ag/rebase-i-in-c, was Re: What's cooking in git.git (Aug 2018, #05; Mon, 20)

> * ag/rebase-i-in-c (2018-08-10) 20 commits
>  - rebase -i: move rebase--helper modes to rebase--interactive
>  - rebase -i: remove git-rebase--interactive.sh
>  - rebase--interactive2: rewrite the submodes of interactive rebase in C
>  - rebase -i: implement the main part of interactive rebase as a builtin
>  - rebase -i: rewrite init_basic_state() in C
>  - rebase -i: rewrite write_basic_state() in C
>  - rebase -i: rewrite the rest of init_revisions_and_shortrevisions() in C
>  - rebase -i: implement the logic to initialize $revisions in C
>  - rebase -i: remove unused modes and functions
>  - rebase -i: rewrite complete_action() in C
>  - t3404: todo list with commented-out commands only aborts
>  - sequencer: change the way skip_unnecessary_picks() returns its result
>  - sequencer: refactor append_todo_help() to write its message to a buffer
>  - rebase -i: rewrite checkout_onto() in C
>  - rebase -i: rewrite setup_reflog_action() in C
>  - sequencer: add a new function to silence a command, except if it fails
>  - rebase -i: rewrite the edit-todo functionality in C
>  - editor: add a function to launch the sequence editor
>  - rebase -i: rewrite append_todo_help() in C
>  - sequencer: make three functions and an enum from sequencer.c public
> 
>  Rewrite of the remaining "rebase -i" machinery in C.
> 
>  With "rebase -i" machinery being rewritten to C, with a different
>  interface between "rebase" proper and its backends, this and the
>  other topics need a bit more work to play with each other better.