mainOpts :: Parser Command
mainOpts = mainCommand

mainOpts :: Parser (Config Build, Command)
mainOpts = (,) <$> configOpts <*> mainCommand
configOpts :: Parser (Config Build)
configOpts = Config . Build . Last . Just <$> dataFileOpt

dataFileOpt :: Parser (Maybe FilePath)
dataFileOpt = optional $ strOption (long "data-file" <> short 'f' <> metavar "FILE")

    options <- execParser opts
    print options

    (config, command) <- execParser opts
    print command