Add Haskell script trying to reproduce the build

We add a Haskell script in charge of reproducing the build.

ReproTest.hs

@@ -20,20 +20,21 @@ import System.Process
 data Config = Config
   { pkgName :: Text,
     ghcPath :: Text }
+data ReproStatus = ReproStatus IsReproducible ReproPaths
 
+type IsReproducible = Bool
 type ReproPaths = [Text]
 type StorePath  = Text
 type NixError   = Text
-type ReproStatus = Maybe ReproPaths
 
 main :: IO ()
 main = do
   c <- execParser opts
   rs <- runExceptT $ repro c
   case rs of
-    Left err -> T.putStr err >> exitFailure
-    Right Nothing -> T.putStr "SUCCESS" >> exitSuccess
-    Right (Just rp) -> T.putStr $ "Cannot Reproduce build:\n" <> unwords rp
+    Left err -> T.putStrLn err >> exitFailure
+    Right (ReproStatus True xs)  -> T.putStrLn "SUCCESS" >> exitSuccess
+    Right (ReproStatus False xs) -> T.putStr $ "Cannot Reproduce build:\n" <> unwords xs
   where
     opts = info (configParser <**> helper)
        ( fullDesc
@@ -61,11 +62,7 @@ repro c = do
   (ecr2, p2) <- streamRunCmd "nix-store"
     ["--realise", "--quiet", "-K", "--check", drvPath] False
   -- 4. If exit code > 1 => Just two repro paths
-  if ecr2 == E.ExitSuccess
-    then pure Nothing
-    else pure $ Just [ p1, p2 ]
-
-
+  pure $ ReproStatus (ecr2 == E.ExitSuccess) [p1, p2]
 
 runDiffoscope :: ReproPaths -> IO StorePath
 runDiffoscope = undefined