Main.hs

import Paths_hdoit (version)
import Data.Version (showVersion)
import Options.Applicative

data Arguments = Arguments
               { version :: Bool,
                 argCommand :: Command
               } deriving Show
data Command = Add (Maybe String) | Base deriving Show

comparser = (Arguments <$> (switch $ long "version") <*>)

addOpt = comparser $ Add <$> (optional $ strOption $ long "foo")

argparser = (comparser $ pure Base) <|>
            subparser
            ( command "add" (info addOpt fullDesc))

-- main = putStrLn $ showVersion version
main = execParser (info argparser fullDesc) >>= print
-- main = print $ Options {optCommand = Base}