RawFilePath conversion of System.Directory

By using System.Directory.OsPath, which takes and returns OsString,
which is a ShortByteString. So, things like dirContents currently have the
overhead of copying that to a ByteString, but that should be less than
the overhead of using Strings which often in turn were converted to
RawFilePaths.

Added Utility.OsString and the OsString build flag. That flag is turned
on in the stack.yaml, and will be turned on automatically by cabal when
built with new enough libraries. The stack.yaml change is a bit ugly,
and that could be reverted for now if it causes any problems.

Note that Utility.OsString.toOsString on windows is avoiding only a
check of encoding that is documented as being unlikely to fail. I don't
think it can fail in git-annex; if it could, git-annex didn't contain
such an encoding check before, so at worst that should be a wash.

Command/Uninit.hs

@@ -102,14 +102,14 @@ startCheckIncomplete recordnotok file key =
 removeAnnexDir :: CommandCleanup -> CommandStart
 removeAnnexDir recordok = do
 	Annex.Queue.flush
-	annexdir <- fromRawFilePath <$> fromRepo gitAnnexDir
+	annexdir <- fromRepo gitAnnexDir
 	annexobjectdir <- fromRepo gitAnnexObjectDir
 	starting ("uninit objects") (ActionItemOther Nothing) (SeekInput []) $ do
 		leftovers <- removeUnannexed =<< listKeys InAnnex
 		prepareRemoveAnnexDir annexdir
 		if null leftovers
 			then do
-				liftIO $ removeDirectoryRecursive annexdir
+				liftIO $ removeDirectoryRecursive (fromRawFilePath annexdir)
 				next recordok
 			else giveup $ unlines
 				[ "Not fully uninitialized"
@@ -134,15 +134,15 @@ removeAnnexDir recordok = do
  -
  - Also closes sqlite databases that might be in the directory,
  - to avoid later failure to write any cached changes to them. -}
-prepareRemoveAnnexDir :: FilePath -> Annex ()
+prepareRemoveAnnexDir :: RawFilePath -> Annex ()
 prepareRemoveAnnexDir annexdir = do
 	Database.Keys.closeDb
 	liftIO $ prepareRemoveAnnexDir' annexdir
 
-prepareRemoveAnnexDir' :: FilePath -> IO ()
+prepareRemoveAnnexDir' :: RawFilePath -> IO ()
 prepareRemoveAnnexDir' annexdir =
 	emptyWhenDoesNotExist (dirTreeRecursiveSkipping (const False) annexdir)
-		>>= mapM_ (void . tryIO . allowWrite . toRawFilePath)
+		>>= mapM_ (void . tryIO . allowWrite)
 
 {- Keys that were moved out of the annex have a hard link still in the
  - annex, with > 1 link count, and those can be removed.