Re: [GSoC][PATCH 2/3] rebase -i: rewrite setup_reflog_action() in C

> This rewrites setup_reflog_action() from shell to C.
> 
> A new command is added to rebase--helper.c, “setup-reflog”, as such as a
> new flag, “verbose”, to silence the output of the checkout operation
> called by setup_reflog_action().

> The shell version is then stripped in favour of a call to the helper. As
> $GIT_REFLOG_ACTION is not longer set at the first call of
> checkout_onto(), a call to comment_for_reflog() is added at the
> beginning of this function.
> 
> Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
> ---
>   builtin/rebase--helper.c   |  9 +++++++--
>   git-rebase--interactive.sh | 16 ++--------------
>   sequencer.c                | 31 +++++++++++++++++++++++++++++++
>   sequencer.h                |  3 +++
>   4 files changed, 43 insertions(+), 16 deletions(-)
> 
> diff --git a/builtin/rebase--helper.c b/builtin/rebase--helper.c
> index d2990b210..d677fb663 100644
> --- a/builtin/rebase--helper.c
> +++ b/builtin/rebase--helper.c
> @@ -12,12 +12,12 @@ static const char * const builtin_rebase_helper_usage[] = {
>   int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
>   {
>   	struct replay_opts opts = REPLAY_OPTS_INIT;
> -	unsigned flags = 0, keep_empty = 0, rebase_merges = 0;
> +	unsigned flags = 0, keep_empty = 0, rebase_merges = 0, verbose = 0;
>   	int abbreviate_commands = 0, rebase_cousins = -1;
>   	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
> +		ADD_EXEC, APPEND_TODO_HELP, EDIT_TODO, SETUP_REFLOG
>   	} command = 0;
>   	struct option options[] = {
>   		OPT_BOOL(0, "ff", &opts.allow_ff, N_("allow fast-forward")),
> @@ -27,6 +27,7 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
>   		OPT_BOOL(0, "rebase-merges", &rebase_merges, N_("rebase merge commits")),
>   		OPT_BOOL(0, "rebase-cousins", &rebase_cousins,
>   			 N_("keep original branch points of cousins")),
> +		OPT_BOOL(0, "verbose", &verbose, N_("verbose")),
>   		OPT_CMDMODE(0, "continue", &command, N_("continue rebase"),
>   				CONTINUE),
>   		OPT_CMDMODE(0, "abort", &command, N_("abort rebase"),
> @@ -50,6 +51,8 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
>   		OPT_CMDMODE(0, "edit-todo", &command,
>   			    N_("edit the todo list during an interactive rebase"),
>   			    EDIT_TODO),
> +		OPT_CMDMODE(0, "setup-reflog", &command,
> +			    N_("setup the reflog action"), SETUP_REFLOG),
>   		OPT_END()
>   	};
>   
> @@ -93,5 +96,7 @@ int cmd_rebase__helper(int argc, const char **argv, const char *prefix)
>   		return !!append_todo_help(0, keep_empty);
>   	if (command == EDIT_TODO && argc == 1)
>   		return !!edit_todo_list(flags);
> +	if (command == SETUP_REFLOG && argc == 2)
> +		return !!setup_reflog_action(&opts, argv[1], verbose);
>   	usage_with_options(builtin_rebase_helper_usage, options);
>   }
> diff --git a/git-rebase--interactive.sh b/git-rebase--interactive.sh
> index 2defe607f..048bbf041 100644
> --- a/git-rebase--interactive.sh
> +++ b/git-rebase--interactive.sh
> @@ -72,6 +72,7 @@ collapse_todo_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 $orig_head
> @@ -119,19 +120,6 @@ initiate_action () {
>   	esac
>   }
>   
> -setup_reflog_action () {
> -	comment_for_reflog start
> -
> -	if test ! -z "$switch_to"
> -	then
> -		GIT_REFLOG_ACTION="$GIT_REFLOG_ACTION: checkout $switch_to"
> -		output git checkout "$switch_to" -- ||
> -			die "$(eval_gettext "Could not checkout \$switch_to")"
> -
> -		comment_for_reflog start
> -	fi
> -}
> -
>   init_basic_state () {
>   	orig_head=$(git rev-parse --verify HEAD) || die "$(gettext "No HEAD?")"
>   	mkdir -p "$state_dir" || die "$(eval_gettext "Could not create temporary \$state_dir")"
> @@ -211,7 +199,7 @@ git_rebase__interactive () {
>   		return 0
>   	fi
>   
> -	setup_reflog_action
> +	git rebase--helper --setup-reflog "$switch_to" ${verbose:+--verbose}
>   	init_basic_state
>   
>   	init_revisions_and_shortrevisions
> diff --git a/sequencer.c b/sequencer.c
> index 3437673d2..4bfe29c7b 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -3131,6 +3131,37 @@ static const char *reflog_message(struct replay_opts *opts,
>   	return buf.buf;
>   }
>   
> +static int checkout_base_commit(struct replay_opts *opts, const char *commit,
> +				int verbose, const char *action)
> +{
> +	struct child_process cmd = CHILD_PROCESS_INIT;
> +
> +	cmd.git_cmd = 1;
> +
> +	argv_array_push(&cmd.args, "checkout");
> +	argv_array_push(&cmd.args, commit);
> +	argv_array_pushf(&cmd.env_array, GIT_REFLOG_ACTION "=%s", action);
> +
> +	if (verbose)
> +		return run_command(&cmd);
> +	else
> +		return run_command_silent_on_success(&cmd);
> +}
> +
> +int setup_reflog_action(struct replay_opts *opts, const char *commit,
> +			int verbose)
> +{
> +	const char *action;
> +
> +	if (commit && *commit) {
> +		action = reflog_message(opts, "start", "checkout %s", commit);
> +		if (checkout_base_commit(opts, commit, verbose, action))
> +			die(_("Could not checkout %s"), commit);
> +	}
> +
> +	return 0;
> +}
> +
>   static const char rescheduled_advice[] =
>   N_("Could not execute the todo command\n"
>   "\n"
> diff --git a/sequencer.h b/sequencer.h
> index 35730b13e..55e4057d8 100644
> --- a/sequencer.h
> +++ b/sequencer.h
> @@ -100,6 +100,9 @@ int update_head_with_reflog(const struct commit *old_head,
>   void commit_post_rewrite(const struct commit *current_head,
>   			 const struct object_id *new_head);
>   
> +int setup_reflog_action(struct replay_opts *opts, const char *commit,
> +			int verbose);
> +
>   #define SUMMARY_INITIAL_COMMIT   (1 << 0)
>   #define SUMMARY_SHOW_AUTHOR_DATE (1 << 1)
>   void print_commit_summary(const char *prefix, const struct object_id *oid,
>