reflog: assert PARSE_OPT_NONEG in parse-options callbacks

In the spirit of 517fe807d6 (assert NOARG/NONEG behavior of
parse-options callbacks, 2018-11-05), this asserts that our callbacks
were invoked using the right flags (since otherwise they'd segfault on
the NULL arg). Both cases are already correct here, so this is mostly
about annotating the functions, and appeasing -Wunused-parameters.

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

builtin/reflog.c

@@ -193,6 +193,8 @@ static int expire_unreachable_callback(const struct option *opt,
 {
 	struct cmd_reflog_expire_cb *cmd = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (parse_expiry_date(arg, &cmd->expire_unreachable))
 		die(_("invalid timestamp '%s' given to '--%s'"),
 		    arg, opt->long_name);
@@ -207,6 +209,8 @@ static int expire_total_callback(const struct option *opt,
 {
 	struct cmd_reflog_expire_cb *cmd = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (parse_expiry_date(arg, &cmd->expire_total))
 		die(_("invalid timestamp '%s' given to '--%s'"),
 		    arg, opt->long_name);