Fix doc in non-cabal projects

..man those non-cabal projects are really getting me down. Who uses
those anwayways ;)

test/CabalHelperSpec.hs

@@ -91,6 +91,6 @@ spec = do
                 (s, s') <- runD $ do
                     Just stack <- getCustomPkgDbStack
                     withCabal $ do
-                        stack' <- getPackageDbStack'
+                        stack' <- getCabalPackageDbStack
                         return (stack, stack')
                 s' `shouldBe` s

test/GhcPkgSpec.hs

@@ -0,0 +1,30 @@
+module GhcPkgSpec where
+
+import Control.Arrow
+import Control.Applicative
+import Distribution.Helper
+import Language.Haskell.GhcMod.GhcPkg
+import Language.Haskell.GhcMod.PathsAndFiles
+import Language.Haskell.GhcMod.CabalHelper
+import Language.Haskell.GhcMod.Error
+import Test.Hspec
+import System.Directory
+import System.FilePath
+import System.Process (readProcess, system)
+
+import Dir
+import TestUtils
+import Data.List
+
+spec :: Spec
+spec = do
+    describe "getPackageDbStack'" $ do
+        it "fixes out of sync custom pkg-db stack" $ do
+            withDirectory_ "test/data/custom-cradle" $ do
+                _ <- system "cabal configure"
+                (s, s') <- runD $ do
+                    Just stack <- getCustomPkgDbStack
+                    withCabal $ do
+                        stack' <- getPackageDbStack
+                        return (stack, stack')
+                s' `shouldBe` s