Re: [PATCH 04/15] sequencer: refactor sequencer_add_exec_commands() to work on a todo_list

> This refactors sequencer_add_exec_commands() to work on a todo_list to
> avoid redundant reads and writes to the disk.
> 
> sequencer_add_exec_commands() still reads the todo list from the disk,
> as it is needed by rebase -p.  todo_list_add_exec_commands() works on a
> todo_list structure, and reparses it at the end.
> 
> Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
> ---
>   sequencer.c | 56 +++++++++++++++++++++++++++++++----------------------
>   1 file changed, 33 insertions(+), 23 deletions(-)
> 
> diff --git a/sequencer.c b/sequencer.c
> index 8dda61927c..6d998f21a4 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -4370,34 +4370,21 @@ int sequencer_make_script(FILE *out, int argc, const char **argv,
>   	return 0;
>   }
>   
> -/*
> - * Add commands after pick and (series of) squash/fixup commands
> - * in the todo list.
> - */
> -int sequencer_add_exec_commands(const char *commands)
> +static void todo_list_add_exec_commands(struct todo_list *todo_list,
> +					const char *commands)
>   {
> -	const char *todo_file = rebase_path_todo();
> -	struct todo_list todo_list = TODO_LIST_INIT;
> -	struct strbuf *buf = &todo_list.buf;
> +	struct strbuf *buf = &todo_list->buf;
>   	size_t offset = 0, commands_len = strlen(commands);
>   	int i, insert;
>   
> -	if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
> -		return error(_("could not read '%s'."), todo_file);
> -
> -	if (todo_list_parse_insn_buffer(todo_list.buf.buf, &todo_list)) {
> -		todo_list_release(&todo_list);
> -		return error(_("unusable todo list: '%s'"), todo_file);
> -	}
> -
>   	/*
>   	 * Insert <commands> after every pick. Here, fixup/squash chains
>   	 * are considered part of the pick, so we insert the commands *after*
>   	 * those chains if there are any.
>   	 */
>   	insert = -1;
> -	for (i = 0; i < todo_list.nr; i++) {
> -		enum todo_command command = todo_list.items[i].command;
> +	for (i = 0; i < todo_list->nr; i++) {
> +		enum todo_command command = todo_list->items[i].command;
>   
>   		if (insert >= 0) {
>   			/* skip fixup/squash chains */
> @@ -4408,7 +4395,7 @@ int sequencer_add_exec_commands(const char *commands)
>   				continue;
>   			}
>   			strbuf_insert(buf,
> -				      todo_list.items[insert].offset_in_buf +
> +				      todo_list->items[insert].offset_in_buf +
>   				      offset, commands, commands_len);
>   			offset += commands_len;
>   			insert = -1;
> @@ -4419,15 +4406,38 @@ int sequencer_add_exec_commands(const char *commands)
>   	}
>   
>   	/* insert or append final <commands> */
> -	if (insert >= 0 && insert < todo_list.nr)
> -		strbuf_insert(buf, todo_list.items[insert].offset_in_buf +
> +	if (insert >= 0 && insert < todo_list->nr)
> +		strbuf_insert(buf, todo_list->items[insert].offset_in_buf +
>   			      offset, commands, commands_len);
>   	else if (insert >= 0 || !offset)
>   		strbuf_add(buf, commands, commands_len);
>   
> -	i = write_message(buf->buf, buf->len, todo_file, 0);
> +	if (todo_list_parse_insn_buffer(buf->buf, todo_list))
> +		BUG("unusable todo list");}

> +
> +/*
> + * Add commands after pick and (series of) squash/fixup commands
> + * in the todo list.
> + */
> +int sequencer_add_exec_commands(const char *commands)
> +{
> +	const char *todo_file = rebase_path_todo();
> +	struct todo_list todo_list = TODO_LIST_INIT;
> +	int res;
> +
> +	if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
> +		return error(_("could not read '%s'."), todo_file);
> +
> +	if (todo_list_parse_insn_buffer(todo_list.buf.buf, &todo_list)) {
> +		todo_list_release(&todo_list);
> +		return error(_("unusable todo list: '%s'"), todo_file);
> +	}
> +
> +	todo_list_add_exec_commands(&todo_list, commands);
> +	res = write_message(todo_list.buf.buf, todo_list.buf.len, todo_file, 0);
>   	todo_list_release(&todo_list);
> -	return i;
> +
> +	return res;
>   }
>   
>   int transform_todos(unsigned flags)
>