From 7ec72e3874a204bd32951be1cd35af85daa7c159 Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@joeyh.name>
Date: Tue, 16 May 2017 11:33:53 -0400
Subject: [PATCH] optimisation

Avoids N^2 list traversal.
---
 Utility/Directory.hs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Utility/Directory.hs b/Utility/Directory.hs
index 693e77131e..c24f36da56 100644
--- a/Utility/Directory.hs
+++ b/Utility/Directory.hs
@@ -96,10 +96,10 @@ dirTreeRecursiveSkipping skipdir topdir = go [] [topdir]
 	go c (dir:dirs)
 		| skipdir (takeFileName dir) = go c dirs
 		| otherwise = unsafeInterleaveIO $ do
-			subdirs <- go c
+			subdirs <- go []
 				=<< filterM (isDirectory <$$> getSymbolicLinkStatus)
 				=<< catchDefaultIO [] (dirContents dir)
-			go (subdirs++[dir]) dirs
+			go (subdirs++dir:c) dirs
 
 {- Moves one filename to another.
  - First tries a rename, but falls back to moving across devices if needed. -}