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

Command/Info.hs

@@ -532,8 +532,9 @@ cachedRemoteData u = do
 			let combinedata d uk = finishCheck uk >>= \case
 				Nothing -> return d
 				Just k -> return $ addKey k d
-			v <- lift $ foldM combinedata emptyKeyInfo
-				=<< loggedKeysFor' u
+			(ks, cleanup) <- lift $ loggedKeysFor' u
+			v <- lift $ foldM combinedata emptyKeyInfo ks
+			liftIO $ void cleanup
 			put s { repoData = M.insert u v (repoData s) }
 			return v