sequencer: report when noop has an argument

The noop command cannot accept any argument, but we never told the user
about any bogus argument. Fix that.

while at it, mention clearly when an argument is required but missing
(for commands *other* than noop).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

sequencer.c

@@ -1261,18 +1261,23 @@ static int parse_insn_line(struct todo_item *item, const char *bol, char *eol)
 	if (i >= TODO_COMMENT)
 		return -1;
 
+	/* Eat up extra spaces/ tabs before object name */
+	padding = strspn(bol, " \t");
+	bol += padding;
+
 	if (item->command == TODO_NOOP) {
+		if (bol != eol)
+			return error(_("%s does not accept arguments: '%s'"),
+				     command_to_string(item->command), bol);
 		item->commit = NULL;
 		item->arg = bol;
 		item->arg_len = eol - bol;
 		return 0;
 	}
 
-	/* Eat up extra spaces/ tabs before object name */
-	padding = strspn(bol, " \t");
 	if (!padding)
-		return -1;
+		return error(_("missing arguments for %s"),
-	bol += padding;
+			     command_to_string(item->command));
 
 	if (item->command == TODO_EXEC) {
 		item->commit = NULL;