OptionParser is a complex piece of software, which can be used to express quite clearly what the user can enter.

There are many sub-tasks to this, and each could be its own PR:

• Turn the optional values into requireds, where needed
• See if the RegExp type coercions can be used
• See if the TrueClass, FalseClass type coercions can be used
• Try to break up setup_parser in some useful way

Resources

• Blog post about OptionParser with examples
• Codeclimate view of the complex Parser class