config: set help text for --bool-or-int

The conversion to parse_opt left this as NULL; on glibc
systems, the usage message prints

   --bool-or-int   (null)

and on other ones, segfaults.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-config.c

@@ -68,7 +68,7 @@ static struct option builtin_config_options[] = {
 	OPT_GROUP("Type"),
 	OPT_BIT(0, "bool", &types, "value is \"true\" or \"false\"", TYPE_BOOL),
 	OPT_BIT(0, "int", &types, "value is decimal number", TYPE_INT),
-	OPT_BIT(0, "bool-or-int", &types, NULL, TYPE_BOOL_OR_INT),
+	OPT_BIT(0, "bool-or-int", &types, "value is --bool or --int", TYPE_BOOL_OR_INT),
 	OPT_GROUP("Other"),
 	OPT_BOOLEAN('z', "null", &end_null, "terminate values with NUL byte"),
 	OPT_END(),