explicitly wait for a git process

Eliminate a zombie that was only cleaned up by the later zombie cleanup
code.

This is still not ideal, it would be cleaner if it used conduit or
something, and if the thread gets killed before waiting, it won't stop
the process.

Only remaining zombies are in CmdLine.Seek

Logs/Location.hs

@@ -126,14 +126,15 @@ finishCheck (Unchecked a) = a
  -
  - Keys that have been marked as dead are not included.
  -}
-loggedKeys :: Annex [Unchecked Key]
+loggedKeys :: Annex ([Unchecked Key], IO Bool)
 loggedKeys = loggedKeys' (not <$$> checkDead)
 
-loggedKeys' :: (Key -> Annex Bool) -> Annex [Unchecked Key]
+loggedKeys' :: (Key -> Annex Bool) -> Annex ([Unchecked Key], IO Bool)
 loggedKeys' check = do
 	config <- Annex.getGitConfig
-	mapMaybe (defercheck <$$> locationLogFileKey config)
-		<$> Annex.Branch.files
+	(bfs, cleanup) <- Annex.Branch.files
+	let l = mapMaybe (defercheck <$$> locationLogFileKey config) bfs
+	return (l, cleanup)
   where
 	defercheck k = Unchecked $ ifM (check k)
 		( return (Just k)
@@ -146,9 +147,13 @@ loggedKeys' check = do
  - This does not stream well; use loggedKeysFor' for lazy streaming.
  -}
 loggedKeysFor :: UUID -> Annex [Key]
-loggedKeysFor u = catMaybes <$> (mapM finishCheck =<< loggedKeysFor' u)
+loggedKeysFor u = do
+	(l, cleanup) <- loggedKeysFor' u
+	l' <- catMaybes <$> mapM finishCheck l
+	liftIO $ void cleanup
+	return l'
 
-loggedKeysFor' :: UUID -> Annex [Unchecked Key]
+loggedKeysFor' :: UUID -> Annex ([Unchecked Key], IO Bool)
 loggedKeysFor' u = loggedKeys' isthere
   where
 	isthere k = do