Re: [PATCH v8 0/2] builtin/config.c: support `--type=<type>` as preferred alias for `--type`

> Attached is the eighth re-roll of my series to add `--type=<type>` as
> the preferred alternative for `--<type>`.
>
> The main changes since v7 concern handling degenerate cases, such as:
>
>   * git config --type=int --type=bool
>   * git config --type=int --int
>
> We have previously had discussion about whether we should (1) retain the
> error in previous versions when confronted with multiple, conflicting
> type specifiers, (2) ignore the error, in favor of making --<type> and
> --type=<type> true synonyms, or (3) some combination of the two.
>
> I have thought some more about my argument that it would be favorable to
> make "--type=int" and "--int" behave in the same way, and I am no
> longer convinced that my argument makes sense. It's based on the premise
> that "--type=<type>" must _necessarily_ allow multiple invocations, such
> as '--type=int --type=bool', and therefore "--int --bool" should be
> updated to behave the same way.
>
> We are not constrained to this behavior, so in v8, I have taught Git the
> following:
>
>   1. Allow multiple non-conflicting types, such as '--int --int',
>      '--type=int --int', and '--int --type=int'.
>
>   2. Disallow multiple conflicting types, such as '--int --bool',
>      '--type=int --bool', and '--int --type=bool'.
>
>   3. Allow conflicting types following --no-type, such as '--int
>      --no-type --bool', '--type=int --no-type --bool', and '--int
>      --no-type --type=bool'. Note that this does _not_ introduce options
>      such as '--no-int' and whatnot.
>
> This is accomplished by a new locally defined macro called
> OPT_CALLBACK_VALUE, which allows us to reuse option_parse_type() to
> handle --int as well, by sending it through as opt->defval.
>
> I think that the above is the best-of-all-worlds choice, but I am
> curious to hear everyone else's thoughts. Thanks in advance for your
> review.

> diff --git a/builtin/config.c b/builtin/config.c
> index 5c8952a17c..7184c09582 100644
> --- a/builtin/config.c
> +++ b/builtin/config.c
> @@ -61,28 +61,53 @@ static int show_origin;
>  #define TYPE_PATH		4
>  #define TYPE_EXPIRY_DATE	5
>
> +#define OPT_CALLBACK_VALUE(s, l, h, f, i) \
> +	{ OPTION_CALLBACK, (s), (l), NULL, NULL, (h), PARSE_OPT_NOARG | \
> +	PARSE_OPT_NONEG, (f), (i) }
> +
> +static struct option builtin_config_options[];

>  static int option_parse_type(const struct option *opt, const char *arg,
>  			     int unset)
>  {
> -	int *type = opt->value;
> -
>  	if (unset) {
> -		*type = 0;
> +		type = 0;
>  		return 0;
>  	}
>
> -	if (!strcmp(arg, "bool"))
> -		*type = TYPE_BOOL;
> -	else if (!strcmp(arg, "int"))
> -		*type = TYPE_INT;
> -	else if (!strcmp(arg, "bool-or-int"))
> -		*type = TYPE_BOOL_OR_INT;
> -	else if (!strcmp(arg, "path"))
> -		*type = TYPE_PATH;
> -	else if (!strcmp(arg, "expiry-date"))
> -		*type = TYPE_EXPIRY_DATE;
> -	else
> -		die(_("unrecognized --type argument, %s"), arg);
> +	/*
> +	 * To support '--<type>' style flags, begin with new_type equal to
> +	 * opt->defval.
> +	 */
> +	int new_type = opt->defval;
> +	if (!new_type) {
> +		if (!strcmp(arg, "bool"))
> +			new_type = TYPE_BOOL;
> +		else if (!strcmp(arg, "int"))
> +			new_type = TYPE_INT;
> +		else if (!strcmp(arg, "bool-or-int"))
> +			new_type = TYPE_BOOL_OR_INT;
> +		else if (!strcmp(arg, "path"))
> +			new_type = TYPE_PATH;
> +		else if (!strcmp(arg, "expiry-date"))
> +			new_type = TYPE_EXPIRY_DATE;
> +		else
> +			die(_("unrecognized --type argument, %s"), arg);
> +	}
> +
> +	if (type != 0 && type != new_type) {
> +		/*
> +		 * Complain when there is a new type not equal to the old type.
> +		 * This allows for combinations like '--int --type=int' and
> +		 * '--type=int --type=int', but disallows ones like '--type=bool
> +		 * --int' and '--type=bool
> +		 * --type=int'.
> +		 */
> +		error("only one type at a time.");
> +		usage_with_options(builtin_config_usage,
> +			builtin_config_options);
> +	}
> +	type = new_type;