git config: don't allow --get-color* and variable type

Doing so would be incoherent since --get-color would pick a color slot
and ignore the variable type option (e.g. --bool), and the type would
require a variable name.

Suggested by Junio C Hamano.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-config.c

@@ -360,6 +360,11 @@ int cmd_config(int argc, const char **argv, const char *unused_prefix)
 	if (get_colorbool_slot)
 	    actions |= ACTION_GET_COLORBOOL;
 
+	if ((get_color_slot || get_colorbool_slot) && types) {
+		error("--get-color and variable type are incoherent");
+		usage_with_options(builtin_config_usage, builtin_config_options);
+	}
+
 	if (HAS_MULTI_BITS(actions)) {
 		error("only one action at a time.");
 		usage_with_options(builtin_config_usage, builtin_config_options);