update for DiffTree type change

Experimentally, using the raw TopFilePath was right here.

Command/Unused.hs

@@ -36,6 +36,7 @@ import qualified Annex.Branch
 import qualified Option
 import Annex.CatFile
 import Types.Key
+import Git.FilePath
 
 def :: [Command]
 def = [withOptions [fromOption] $ command "unused" paramNothing seek
@@ -293,9 +294,9 @@ withKeysReferencedInGitRef a ref = do
 	forM_ ts $ tKey lookAtWorkingTree >=> maybe noop a
 	liftIO $ void clean
   where
-	tKey True = fmap fst <$$> Backend.lookupFile . DiffTree.file
+	tKey True = fmap fst <$$> Backend.lookupFile . getTopFilePath . DiffTree.file
 	tKey False = fileKey . takeFileName . encodeW8 . L.unpack <$$>
-		catFile ref . DiffTree.file
+		catFile ref . getTopFilePath . DiffTree.file
 
 {- Looks in the specified directory for bad/tmp keys, and returns a list
  - of those that might still have value, or might be stale and removable.