`autoprintHelpAndExit` doesn't print the help message and exit when `--help` is passed to a subcommand

[jnowjack-lucidchart]

When using multiple main methods --help is not automatically detected if passed to a subcommand.

For example:

object Main {
  @main def foo(@arg() bar: Boolean ) = {}
  @main def baz() = {}
  def main(args: Array[String]): Unit = ParserForMethods(this).runOrExit(args.toSeq)
}

When run with ./example foo --help will error instead of printing the help message for foo:

Missing argument: --bar <bool>
Unknown argument: "--help"
Expected Signature: foo
  --bar <bool>

The --help arg will also get swallowed by a Leftover[String] or String* and the command will run instead of immediately exiting:

object Main {
  @main def foo(@arg() bar: String*) = { println(bar) }
  @main def bar() = {}
  def main(args: Array[String]): Unit = ParserForMethods(this).runOrExit(args.toSeq)
}

When run with ./example foo --help outputs:
List(--help)