avoid closing pipe before all the shas are read from it

Could have just used hGetContentsStrict here, but that would require
storing all the shas in memory. Since this is called at the end of a
git-annex run, it may have created a *lot* of shas, so I avoid that memory
use and stream them out like before.

Annex/Branch.hs

@@ -291,9 +291,10 @@ stageJournal = do
 	withIndex $ liftIO $ do
 		let dir = gitAnnexJournalDir g
 		let paths = map (dir </>) fs
-		shas <- Git.HashObject.hashFiles paths g
+		(shas, cleanup) <- Git.HashObject.hashFiles paths g
 		Git.UnionMerge.update_index g $
 			index_lines shas (map fileJournal fs)
+		cleanup
 		mapM_ removeFile paths
 	where
 		index_lines shas = map genline . zip shas

Git/HashObject.hs

@@ -10,16 +10,15 @@ module Git.HashObject where
 import Common
 import Git
 
-{- Injects a set of files into git, returning the shas of the objects. -}
+{- Injects a set of files into git, returning the shas of the objects
-hashFiles :: [FilePath] -> Repo -> IO [Sha]
+ - and an IO action to call ones the the shas have been used. -}
+hashFiles :: [FilePath] -> Repo -> IO ([Sha], IO ())
 hashFiles paths repo = do
 	(pid, fromh, toh) <- hPipeBoth "git" $ toCommand $ git_hash_object repo
 	_ <- forkProcess (feeder toh)
 	hClose toh
-	shas <- map Git.Ref . lines <$> hGetContents fromh
+	shas <- map Git.Ref . lines <$> hGetContentsStrict fromh
-	hClose fromh
+	return (shas, ender fromh pid)
-	forceSuccess pid
-	return shas
 	where
 		git_hash_object = Git.gitCommandLine
 			[Param "hash-object", Param "-w", Param "--stdin-paths"]
@@ -27,3 +26,6 @@ hashFiles paths repo = do
 			hPutStr toh $ unlines paths
 			hClose toh
 			exitSuccess
+		ender fromh pid = do
+			hClose fromh
+			forceSuccess pid