reflog delete: narrow scope of "cmd" passed to count_reflog_ent()

Change the "cb_data" we pass to the count_reflog_ent() to be the
&cb.cmd itself, instead of passing &cb and having the callback lookup
cb->cmd.

This makes it clear that the "cb" itself is the same memzero'd
structure on each iteration of the for-loop that uses &cb, except for
the "cmd" member.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/reflog.c

@@ -662,20 +662,18 @@ static int count_reflog_ent(struct object_id *ooid, struct object_id *noid,
 		const char *email, timestamp_t timestamp, int tz,
 		const char *message, void *cb_data)
 {
-	struct expire_reflog_policy_cb *cb = cb_data;
-	if (!cb->cmd.expire_total || timestamp < cb->cmd.expire_total)
-		cb->cmd.recno++;
+	struct cmd_reflog_expire_cb *cb = cb_data;
+	if (!cb->expire_total || timestamp < cb->expire_total)
+		cb->recno++;
 	return 0;
 }
 
 static int cmd_reflog_delete(int argc, const char **argv, const char *prefix)
 {
-	struct expire_reflog_policy_cb cb;
+	struct cmd_reflog_expire_cb cmd = { 0 };
 	int i, status = 0;
 	unsigned int flags = 0;
 
-	memset(&cb, 0, sizeof(cb));
-
 	for (i = 1; i < argc; i++) {
 		const char *arg = argv[i];
 		if (!strcmp(arg, "--dry-run") || !strcmp(arg, "-n"))
@@ -703,6 +701,7 @@ static int cmd_reflog_delete(int argc, const char **argv, const char *prefix)
 		const char *spec = strstr(argv[i], "@{");
 		char *ep, *ref;
 		int recno;
+		struct expire_reflog_policy_cb cb = { 0 };
 
 		if (!spec) {
 			status |= error(_("not a reflog: %s"), argv[i]);
@@ -716,14 +715,15 @@ static int cmd_reflog_delete(int argc, const char **argv, const char *prefix)
 
 		recno = strtoul(spec + 2, &ep, 10);
 		if (*ep == '}') {
-			cb.cmd.recno = -recno;
-			for_each_reflog_ent(ref, count_reflog_ent, &cb);
+			cmd.recno = -recno;
+			for_each_reflog_ent(ref, count_reflog_ent, &cmd);
 		} else {
-			cb.cmd.expire_total = approxidate(spec + 2);
-			for_each_reflog_ent(ref, count_reflog_ent, &cb);
-			cb.cmd.expire_total = 0;
+			cmd.expire_total = approxidate(spec + 2);
+			for_each_reflog_ent(ref, count_reflog_ent, &cmd);
+			cmd.expire_total = 0;
 		}
 
+		cb.cmd = cmd;
 		status |= reflog_expire(ref, flags,
 					reflog_expiry_prepare,
 					should_expire_reflog_ent,