udevadm-settle: reject positional arguments

The settle command does not define positional arguments.

Reject them during argument parsing instead of silently ignoring
them.

Reproducer:
  udevadm settle /no/such/argument

Before:
  The command exits successfully and ignores the argument.

Follow-up:
  c71509028f

src/udev/udevadm-settle.c

@@ -88,6 +88,10 @@ static int parse_argv(int argc, char *argv[]) {
                                               opts.opt->short_code);
                 }
 
+        if (option_parser_get_n_args(&opts) > 0)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "This subprogram takes no positional arguments.");
+
         return 1;
 }
 

test/units/TEST-17-UDEV.sanity-check.sh

@@ -152,6 +152,7 @@ udevadm monitor -h
 udevadm settle
 udevadm settle -t 5
 udevadm settle -E /sys/class/net/$netdev
+(! udevadm settle /no/such/argument)
 udevadm settle -h
 
 udevadm test /dev/null