This function is too long for an anonymous in-line function. Please extract it into a proper named function, e.g. `convertArgValueToArray`. Consider doing the same for other functions too, for example you have two copies of the same function for string to int conversion.

I suggest you to extract the code for the definition of command-line options to a standalone file in lib:
- the new file will be a natural home for the new conversion functions,
- `bin/index.js` will be much shorter and simpler,
- it will be possible to write unit-tests for configuration-related code.