move hashObject to HashObject library and generalize it to support all git object types

Git/UnionMerge.hs

@@ -10,7 +10,6 @@ module Git.UnionMerge (
 	merge_index
 ) where
 
-import System.Cmd.Utils
 import qualified Data.Text.Lazy as L
 import qualified Data.Text.Lazy.Encoding as L
 import qualified Data.Set as S
@@ -21,6 +20,8 @@ import Git.Sha
 import Git.CatFile
 import Git.Command
 import Git.UpdateIndex
+import Git.HashObject
+import Git.Types
 
 {- Performs a union merge between two branches, staging it in the index.
  - Any previously staged changes in the index will be lost.
@@ -72,7 +73,7 @@ mergeFile :: String -> FilePath -> CatFileHandle -> Repo -> IO (Maybe String)
 mergeFile info file h repo = case filter (/= nullSha) [Ref asha, Ref bsha] of
 	[] -> return Nothing
 	(sha:[]) -> use sha
-	shas -> use =<< either return (hashObject repo . unlines) =<<
+	shas -> use =<< either return (hashObject repo BlobObject . unlines) =<<
 		calcMerge . zip shas <$> mapM getcontents shas
 	where
 		[_colonmode, _bmode, asha, bsha, _status] = words info
@@ -80,18 +81,6 @@ mergeFile info file h repo = case filter (/= nullSha) [Ref asha, Ref bsha] of
 			L.decodeUtf8 <$> catObject h s
 		use sha = return $ Just $ update_index_line sha file
 
-{- Injects some content into git, returning its Sha. -}
-hashObject :: Repo -> String -> IO Sha
-hashObject repo content = getSha subcmd $ do
-	(h, s) <- pipeWriteRead (map Param params) content repo
-	length s `seq` do
-		forceSuccess h
-		reap -- XXX unsure why this is needed
-		return s
-	where
-		subcmd = "hash-object"
-		params = [subcmd, "-w", "--stdin"]
-
 {- Calculates a union merge between a list of refs, with contents.
  -
  - When possible, reuses the content of an existing ref, rather than