Re: [GSoC][PATCH 3/3] rebase -i: rewrite checkout_onto() in C

> This rewrites checkout_onto() from shell to C.
> 
> A new command (“checkout-onto”) is added to rebase--helper.c. The shell
> version is then stripped.
> 
> Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
> ---
>   builtin/rebase--helper.c   |  7 ++++++-
>   git-rebase--interactive.sh | 25 ++++---------------------
>   sequencer.c                | 19 +++++++++++++++++++
>   sequencer.h                |  3 +++
>   4 files changed, 32 insertions(+), 22 deletions(-)
> 
> diff --git a/builtin/rebase--helper.c b/builtin/rebase--helper.c
> index d677fb663..f9fffba96 100644
> --- a/builtin/rebase--helper.c
> +++ b/builtin/rebase--helper.c
> @@ -17,7 +17,8 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
>   	enum {
>   		CONTINUE = 1, ABORT, MAKE_SCRIPT, SHORTEN_OIDS, EXPAND_OIDS,
>   		CHECK_TODO_LIST, SKIP_UNNECESSARY_PICKS, REARRANGE_SQUASH,
> -		ADD_EXEC, APPEND_TODO_HELP, EDIT_TODO, SETUP_REFLOG
> +		ADD_EXEC, APPEND_TODO_HELP, EDIT_TODO, SETUP_REFLOG,
> +		CHECKOUT_ONTO
>   	} command = 0;
>   	struct option options[] = {
>   		OPT_BOOL(0, "ff", &opts.allow_ff, N_("allow fast-forward")),
> @@ -53,6 +54,8 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
>   			    EDIT_TODO),
>   		OPT_CMDMODE(0, "setup-reflog", &command,
>   			    N_("setup the reflog action"), SETUP_REFLOG),
> +		OPT_CMDMODE(0, "checkout-onto", &command,
> +			    N_("checkout a commit"), CHECKOUT_ONTO),
>   		OPT_END()
>   	};
>   
> @@ -98,5 +101,7 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
>   		return !!edit_todo_list(flags);
>   	if (command == SETUP_REFLOG && argc == 2)
>   		return !!setup_reflog_action(&opts, argv[1], verbose);
> +	if (command == CHECKOUT_ONTO && argc == 4)
> +		return !!checkout_onto(&opts, argv[1], argv[2], argv[3], verbose);
>   	usage_with_options(builtin_rebase_helper_usage, options);
>   }
> diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
> index 048bbf041..0ae053291 100644
> --- a/git-rebase--interactive.sh
> +++ b/git-rebase--interactive.sh
> @@ -28,17 +28,6 @@ case "$comment_char" in
>   	;;
>   esac
>   
> -orig_reflog_action="$GIT_REFLOG_ACTION"
> -
> -comment_for_reflog () {
> -	case "$orig_reflog_action" in
> -	''|rebase*)
> -		GIT_REFLOG_ACTION="rebase -i ($1)"
> -		export GIT_REFLOG_ACTION
> -		;;
> -	esac
> -}
> -
>   die_abort () {
>   	apply_autostash
>   	rm -rf "$state_dir"
> @@ -70,14 +59,6 @@ collapse_todo_ids() {
>   	git rebase--helper --shorten-ids
>   }
>   
> -# Switch to the branch in $into and notify it in the reflog
> -checkout_onto () {
> -	comment_for_reflog start
> -	GIT_REFLOG_ACTION="$GIT_REFLOG_ACTION: checkout $onto_name"
> -	output git checkout $onto || die_abort "$(gettext "could not detach HEAD")"
> -	git update-ref ORIG_HEAD $orig_head
> -}
> -
>   get_missing_commit_check_level () {
>   	check_level=$(git config --get rebase.missingCommitsCheck)
>   	check_level=${check_level:-ignore}
> @@ -176,7 +157,8 @@ EOF
>   
>   	git rebase--helper --check-todo-list || {
>   		ret=$?
> -		checkout_onto
> +		git rebase--helper --checkout-onto "$onto_name" "$onto" \
> +		    "$orig_head" ${verbose:+--verbose}
>   		exit $ret
>   	}
>   
> @@ -186,7 +168,8 @@ EOF
>   	onto="$(git rebase--helper --skip-unnecessary-picks)" ||
>   	die "Could not skip unnecessary pick commands"
>   
> -	checkout_onto
> +	git rebase--helper --checkout-onto "$onto_name" "$onto" "$orig_head" \
> +	    ${verbose:+--verbose}
>   	require_clean_work_tree "rebase"
>   	exec git rebase--helper ${force_rebase:+--no-ff} $allow_empty_message \
>   	     --continue
> diff --git a/sequencer.c b/sequencer.c
> index 4bfe29c7b..d149cbf92 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -3162,6 +3162,25 @@ int setup_reflog_action(struct replay_opts *opts, const char *commit,
>   	return 0;
>   }
>   
> +int checkout_onto(struct replay_opts *opts,
> +		  const char *onto_name, const char *onto,
> +		  const char *orig_head, unsigned verbose)
> +{
> +	struct object_id oid;
> +	const char *action = reflog_message(opts, "start", "checkout %s", onto_name);
> +
> +	if (get_oid(orig_head, &oid))
> +		die(_("%s: not a valid OID"), orig_head);

> +
> +	if (checkout_base_commit(opts, onto, verbose, action)) {
> +		apply_autostash(opts);
> +		sequencer_remove_state(opts);
> +		die(_("could not detach HEAD"));
> +	}
> +
> +	return update_ref(NULL, "ORIG_HEAD", &oid, NULL, 0, UPDATE_REFS_MSG_ON_ERR);
> +}
> +
>   static const char rescheduled_advice[] =
>   N_("Could not execute the todo command\n"
>   "\n"
> diff --git a/sequencer.h b/sequencer.h
> index 55e4057d8..9899d90fc 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -102,6 +102,9 @@ void commit_post_rewrite(const struct commit *current_head,
>   
>   int setup_reflog_action(struct replay_opts *opts, const char *commit,
>   			int verbose);
> +int checkout_onto(struct replay_opts *opts,
> +		  const char *onto_name, const char *onto,
> +		  const char *orig_head, unsigned verbose);
>   
>   #define SUMMARY_INITIAL_COMMIT   (1 << 0)
>   #define SUMMARY_SHOW_AUTHOR_DATE (1 << 1)
>