Subject: Re: [PATCH 2/2] builtin: use git_read_line_interactively to prompt

From: Junio C Hamano <[email-masked]>
Date: Fri, 14 May 2021 07:51:43 +0900

Firmin Martin <[email-masked]> writes:

> diff --git a/builtin/am.c b/builtin/am.c
> index 8355e3566f..32eae4eb2e 100644
> --- a/builtin/am.c
> +++ b/builtin/am.c
> @@ -1643,7 +1643,7 @@ static int do_interactive(struct am_state *state)
>  	assert(state->msg);
>  
>  	for (;;) {
> -		char reply[64];
> +		struct strbuf reply = STRBUF_INIT;

If you call this reply_strbuf, and introduce "const char *reply",
and ...

>  		puts(_("Commit Body is:"));
>  		puts("--------------------------");
> @@ -1656,17 +1656,17 @@ static int do_interactive(struct am_state *state)
>  		 * input at this point.
>  		 */
>  		printf(_("Apply? [y]es/[n]o/[e]dit/[v]iew patch/[a]ccept all: "));
> -		if (!fgets(reply, sizeof(reply), stdin))
> +		if (git_read_line_interactively(&reply) == EOF)
>  			die("unable to read from stdin; aborting");

... assign "reply = reply_strbuf.buf" here, you do not have to
change anything below.

> -		if (*reply == 'y' || *reply == 'Y') {
> +		if (reply.len && !strncasecmp(reply.buf, "yes", reply.len)) {

And we shouldn't sneak an unrelated change like this into a patch
whose purpose is to allow reading from the standard input instead of
always from "/dev/tty".

As I explained earlier, git_read_line_interactively() is usable only
when we know that the standard input is *not* used for the data we
are operating on and is available to be used for simulating
interactive input.  Since "git am -i" never reads the mailbox from
the standard input, the use of the helper here is acceptable.

> diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
> index 1fdb7d9d10..134347eb39 100644
> --- a/builtin/bisect--helper.c
> +++ b/builtin/bisect--helper.c
> @@ -340,7 +340,7 @@ static int decide_next(const struct bisect_terms *terms,
>  
>  	if (missing_good && !missing_bad &&
>  	    !strcmp(current_term, terms->term_good)) {
> -		char *yesno;
> +		struct strbuf yesno = STRBUF_INIT;
>  		/*
>  		 * have bad (or new) but not good (or old). We could bisect
>  		 * although this is less optimum.
> @@ -353,8 +353,9 @@ static int decide_next(const struct bisect_terms *terms,
>  		 * translation. The program will only accept English input
>  		 * at this point.
>  		 */
> -		yesno = git_prompt(_("Are you sure [Y/n]? "), PROMPT_ECHO);
> -		if (starts_with(yesno, "N") || starts_with(yesno, "n"))
> +		printf(_("Are you sure [Y/n]? "));
> +		git_read_line_interactively(&yesno);

The use of this helper here is also OK as the standard input to "git
bisect" is available for simulating interactive input.

> +		if (yesno.len && !strncasecmp(yesno.buf, "no", yesno.len))
>  			return -1;
>  		return 0;
>  	}

It may make sense to have a thin wrapper around this pattern, e.g.

	static int ask_yesno(const char *question)
	{
		struct strbuf answer = STRBUF_INIT;
		printf("%s [Y/n]? ", question);
		git_read_line_interactively(&answer);
                return !(answer.buf[0] == 'N' || answer.buf[0] == 'n');
	}

so that the above caller can become

		return ask_yesno(_("Are you sure")) ? 0 : -1;

and ...

> -	yesno = git_prompt(_("Do you want me to do it for you "
> -			     "[Y/n]? "), PROMPT_ECHO);
> -	res = tolower(*yesno) == 'n' ?
> +	printf(_("Do you want me to do it for you [Y/n]? "));
> +	git_read_line_interactively(&yesno);
> +	res = (yesno.len && strncasecmp(yesno.buf, "no", yesno.len)) ?
>  		-1 : bisect_start(terms, empty_strvec, 0);

... this caller can become

	if (ask_yesno(_("Do you want me to do it for you")))
		res = bisect_start(terms, empty_strvec, 0);
	else
		res = -1;

Thanks.