`/`‑prefixed args with `=` misparsed as non-existing option

[matthieugicquel]

= is a valid char in a posix cli argument or filesystem paths, but clikt currently doesn't accept it and errors with "no such option".

I come from far away with this issue 🙂. My real-world situation is developing a React Native app, using pnpm's patching feature, which creates folders with =, which google prefab, called by Android Gradle Plugin without a -- before arguments, fails to handle. Prefab uses clikt.

class C : CliktCommand() {
    val x by argument()
    override fun run() = echo(x)
}

C().parse("/some/path-with=sign/foo")

→ Error: no such option /some/path-with

I've looked at the code a little and I know it's complicated as / can be a valid prefix for options. I'm probably missing some things, but it looks like ignoring unknown prefixes when trying to detect options could fix the issue without too many bad side-effects. Something like this:

     private fun isLongOptionWithEquals(prefix: String, token: String): Boolean {
         // ...
+        if (prefix !in prefixes) return false
         return context.transformToken(context, token.take(2)) !in optionsByName
     }

Happy to make a PR if it helps!