I can only encourage to use Haskell for such kinds of problems. This was my first Haskell program and I was productive quite fast thanks to "Learn you a Haskell" and the great Parsec library for parsing the Dockerfile.

If you are an experienced Haskeller I would be very glad if you look over the project and problems in an issue. Because mostly I have no idea whether what I am doing is idiomatic or not.

The code looks good. One thing you might want to consider is using applicative style for parsing. So

  taggedImage :: Parser BaseImage
  taggedImage = do
    name <- many (noneOf ":")
    reservedOp ":"
    tag <- many (noneOf "\n")
    return $ TaggedImage name tag

Would end up something like:

  taggedImage :: Parser BaseImage
  taggedImage = TaggedImage <$> (many (noneOf "\n") <* reservedOp ":")
                            <*> (many (noneOf "\n")

i would be nice to make codeclimate engine out of this. https://docs.codeclimate.com/docs/list-of-engines