ByteString Ref continued

Attoparsec parser for diff-tree.

Changed fromRef back to producing a String, to avoid needing to convert
every use of it. However, this does mean I'm going to miss some
opportunities where fromRef is used and the result converted back to a
ByteString. Would be worth revisiting that at some point maybe.

Git/DiffTreeItem.hs

@@ -10,6 +10,7 @@ module Git.DiffTreeItem (
 ) where
 
 import System.Posix.Types
+import qualified Data.ByteString as S
 
 import Git.FilePath
 import Git.Types
@@ -19,6 +20,6 @@ data DiffTreeItem = DiffTreeItem
 	, dstmode :: FileMode
 	, srcsha :: Sha -- null sha if file was added
 	, dstsha :: Sha -- null sha if file was deleted
-	, status :: String
+	, status :: S.ByteString
 	, file :: TopFilePath
 	} deriving Show