ci: Probe boot packages from package db

Addresses #93.

ci/Main.hs

@@ -7,6 +7,7 @@ import Control.Monad
 import Options.Applicative
 import qualified TestPatches
 import qualified MakeConstraints
+import System.FilePath
 
 mode :: Parser (IO ())
 mode = hsubparser $ mconcat
@@ -16,8 +17,13 @@ mode = hsubparser $ mconcat
   where
     testPatches = TestPatches.testPatches <$> TestPatches.config
     makeConstraints =
-      (MakeConstraints.makeConstraints >=> print)
-      <$> argument str (metavar "DIR" <> help "patches directory")
+      f
+      <$> option str (short 'w' <> long "with-compiler" <> metavar "GHC" <> help "ghc path")
+      <*> argument str (metavar "DIR" <> help "patches directory")
+
+    f ghcPath patchesDir = do
+        let ghcPkgPath = replaceFileName ghcPath "ghc-pkg"
+        MakeConstraints.makeConstraints patchesDir ghcPkgPath >>= print
 
 main :: IO ()
 main = do