Re: [PATCH 1/2] config api: Add git_config_magic_int()

[Junio C Hamano <gitster@pobox.com>]

Andreas Ericsson <ae@op5.se> writes:

> +int git_config_magic_int(const char *name, const char *value,
> +			 const char *magic_value, int magic_setting)
> +{
> +	if (value && !strcasecmp(value, magic_value))
> +		return magic_setting;
> +
> +	return git_config_int(name, value);
> +}

I do not think this has much to do with any "magic".

An instruction "use 0 threads" when taken literally would mean
"do not use any CPU" which would not make much sense.  In that
sense, giving a magic meaning of "guess an appropriate value" to
0 may be a good idea.  A valid alternative would be to make 0
mean the same thing as 1, but that is much more boring ;-)

But if you did so, that means "var = 0" invokes the same magic
as "var = auto".  The magic lives in "0", and not in "auto".

I think the direction your patch leads us is good, but I think
it should allow an array of symbolic ways to spell values to be
useful, that is:

	struct config_symbolic_int {
        	const char *name;
                int value;
	};
        int git_config_symbolic_int(const char *var, const char *value,
				    struct config_symbolic_int *);

That way, you can have

	{ { "high", 9 }, { "default", 0 }, { "low", 1 } };

and say things like "zlevel = high|default|low".