.unconditionalRemaining parsing skips -- in subcommands

[JensAyton]

As documented, the . unconditionalRemaining parsing mode includes -- and any following tokens, when used in a root command. However, in subcommands, the -- is skipped (but the following arguments are included).

ArgumentParser version: 0.0.5 and master
Swift version: Apple Swift version 5.1.3 (swiftlang-1100.0.282.1 clang-1100.0.33.15)

Checklist

• If possible, I've reproduced the issue using the master branch of this package
• I've searched for existing GitHub issues

Steps to Reproduce

This code is adapted from the section Alternative positional argument parsing strategies in the documentation. It adds parsing: .unconditionalRemaining and also wraps the example command so it acts as a subcommand.

import ArgumentParser

struct Example: ParsableCommand {
    @Flag() var verbose: Bool
    @Argument(parsing: .unconditionalRemaining) var files: [String]

    func run() throws {
        print("Verbose: \(verbose), files: \(files)")
    }
}

struct Wrapper: ParsableCommand {

    static let configuration = CommandConfiguration(
        abstract: "yes",
        subcommands: [
            Example.self
        ]
    )
}

Wrapper.main()

Expected behavior

When invoked as wrapper example --verbose file1.swift -- file2.swift --other, it should print:
Verbose: true, files: ["file1.swift", "--", "file2.swift", "--other"]

Actual behavior

It actually prints:
Verbose: true, files: ["file1.swift", "file2.swift", "--other"]

Note that if we replace Wrapper.main() with Example.main() (and remove example from the invocation), it works as expected.