config: make git_configset_get_string_tmp() private

This method was created in f1de981 (config: fix leaks from
git_config_get_string_const(), 2020-08-14) but its only use was in the
repo_config_get_string_tmp() method, also declared in config.h and
implemented in config.c. Since this is otherwise unused and is a very
similar implementation to git_configset_get_value(), let's remove this
declaration.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Reviewed-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: derrickstolee

config.c

@@ -2179,8 +2179,8 @@ int git_configset_get_string(struct config_set *cs, const char *key, char **dest
 		return 1;
 }
 
-int git_configset_get_string_tmp(struct config_set *cs, const char *key,
-				 const char **dest)
+static int git_configset_get_string_tmp(struct config_set *cs, const char *key,
+					const char **dest)
 {
 	const char *value;
 	if (!git_configset_get_value(cs, key, &value)) {

config.h

@@ -494,7 +494,6 @@ void git_configset_clear(struct config_set *cs);
 int git_configset_get_value(struct config_set *cs, const char *key, const char **dest);
 
 int git_configset_get_string(struct config_set *cs, const char *key, char **dest);
-int git_configset_get_string_tmp(struct config_set *cs, const char *key, const char **dest);
 int git_configset_get_int(struct config_set *cs, const char *key, int *dest);
 int git_configset_get_ulong(struct config_set *cs, const char *key, unsigned long *dest);
 int git_configset_get_bool(struct config_set *cs, const char *key, int *dest);