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

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

[Andreas Ericsson]

There are some values where git can reasonably guess at an
optimal value. For such occasions, this is a nifty addendum
to the config api, letting the caller specify a magic string
and a magic setting to return if the value of the variable
matches the magic string.

An example would be for threads, where 0 = auto is overly
voodoo-ish for some consumers, and typing "auto" is much
nicer and more immediately obvious.

Signed-off-by: Andreas Ericsson <ae@op5.se>
---

 cache.h  |    1 +
 config.c |    9 +++++++++
 2 files changed, 10 insertions(+), 0 deletions(-)

diff --git a/cache.h b/cache.h
index 3867ba7..1b923ad 100644
--- a/cache.h
+++ b/cache.h
@@ -623,6 +623,7 @@ extern int git_config(config_fn_t fn);
 extern int git_parse_long(const char *, long *);
 extern int git_parse_ulong(const char *, unsigned long *);
 extern int git_config_int(const char *, const char *);
+extern int git_config_magic_int(const char *, const char *, const char *, int);
 extern unsigned long git_config_ulong(const char *, const char *);
 extern int git_config_bool(const char *, const char *);
 extern int git_config_set(const char *, const char *);
diff --git a/config.c b/config.c
index 3e72778..635d92b 100644
--- a/config.c
+++ b/config.c
@@ -288,6 +288,15 @@ int git_config_int(const char *name, const char *value)
 	return ret;
 }
 
+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);
+}
+
 unsigned long git_config_ulong(const char *name, const char *value)
 {
 	unsigned long ret;
-- 
1.5.4.rc5.11.g0eab8

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

[Junio C Hamano]

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".

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

[Andreas Ericsson]

Junio C Hamano wrote:
> 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".

Good idea. I'll look into it right away. I sorely need a break from
coding backends for webapps anyway. I'll send this one separately and
then tack 2/2 onto the builtin-pack-objects patch thing. That one
should probably be a /3 series anyway, when I come to think of it.

-- 
Andreas Ericsson                   andreas.ericsson@op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231