wip RawFilePath

Goal is to make git-annex faster by using ByteString for all the
worktree traversal. For now, this is focusing on Command.Find,
in order to benchmark how much it helps. (All other commands are
temporarily disabled)

Currently in a very bad unbuildable in-between state.

Git/Ref.hs

@@ -5,6 +5,8 @@
  - Licensed under the GNU AGPL version 3 or higher.
  -}
 
+{-# LANGUAGE OverloadedStrings #-}
+
 module Git.Ref where
 
 import Common
@@ -13,7 +15,8 @@ import Git.Command
 import Git.Sha
 import Git.Types
 
-import Data.Char (chr)
+import Data.Char (chr, ord)
+import qualified Data.ByteString as S
 
 headRef :: Ref
 headRef = Ref "HEAD"
@@ -88,8 +91,10 @@ file ref repo = localGitDir repo </> fromRef ref
  - that was just created. -}
 headExists :: Repo -> IO Bool
 headExists repo = do
-	ls <- lines <$> pipeReadStrict [Param "show-ref", Param "--head"] repo
-	return $ any (" HEAD" `isSuffixOf`) ls
+	ls <- S.split nl <$> pipeReadStrict [Param "show-ref", Param "--head"] repo
+	return $ any (" HEAD" `S.isSuffixOf`) ls
+  where
+	nl = fromIntegral (ord '\n')
 
 {- Get the sha of a fully qualified git ref, if it exists. -}
 sha :: Branch -> Repo -> IO (Maybe Sha)
@@ -100,8 +105,9 @@ sha branch repo = process <$> showref repo
 		, Param "--hash" -- get the hash
 		, Param $ fromRef branch
 		]
-	process [] = Nothing
-	process s = Just $ Ref $ firstLine s
+	process s
+		| S.null s = Nothing
+		| otherwise = Just $ Ref $ decodeBS' $ firstLine' s
 
 headSha :: Repo -> IO (Maybe Sha)
 headSha = sha headRef
@@ -116,7 +122,7 @@ matchingWithHEAD refs repo = matching' ("--head" : map fromRef refs) repo
 
 {- List of (shas, branches) matching a given ref spec. -}
 matching' :: [String] -> Repo -> IO [(Sha, Branch)]
-matching' ps repo = map gen . lines <$> 
+matching' ps repo = map gen . lines . decodeBS' <$> 
 	pipeReadStrict (Param "show-ref" : map Param ps) repo
   where
 	gen l = let (r, b) = separate (== ' ') l
@@ -148,7 +154,7 @@ delete oldvalue ref = run
  - The ref may be something like a branch name, and it could contain
  - ":subdir" if a subtree is wanted. -}
 tree :: Ref -> Repo -> IO (Maybe Sha)
-tree (Ref ref) = extractSha <$$> pipeReadStrict
+tree (Ref ref) = extractSha . decodeBS <$$> pipeReadStrict
 	[ Param "rev-parse", Param "--verify", Param "--quiet", Param ref' ]
   where
 	ref' = if ":" `isInfixOf` ref