add catFileIndex

Annex/CatFile.hs

@@ -7,6 +7,7 @@
 
 module Annex.CatFile (
 	catFile,
+	catFileIndex,
 	catObject,
 	catObjectDetails,
 	catFileHandle
@@ -25,6 +26,11 @@ catFile branch file = do
 	h <- catFileHandle
 	liftIO $ Git.CatFile.catFile h branch file
 
+catFileIndex :: FilePath -> Annex L.ByteString
+catFileIndex file = do
+	h <- catFileHandle
+	liftIO $ Git.CatFile.catFileIndex h file
+
 catObject :: Git.Ref -> Annex L.ByteString
 catObject ref = do
 	h <- catFileHandle

Git/CatFile.hs

@@ -10,6 +10,7 @@ module Git.CatFile (
 	catFileStart,
 	catFileStop,
 	catFile,
+	catFileIndex,
 	catObject,
 	catObjectDetails,
 ) where
@@ -40,6 +41,10 @@ catFileStop = CoProcess.stop
 catFile :: CatFileHandle -> Branch -> FilePath -> IO L.ByteString
 catFile h branch file = catObject h $ Ref $ show branch ++ ":" ++ file
 
+{- Reads a file from the index. -}
+catFileIndex :: CatFileHandle -> FilePath -> IO L.ByteString
+catFileIndex h file = catObject h $ Ref $ ':' : file
+
 {- Uses a running git cat-file read the content of an object.
  - Objects that do not exist will have "" returned. -}
 catObject :: CatFileHandle -> Ref -> IO L.ByteString