mercurial/util.py

--- a/mercurial/util.py	Sat May 06 04:51:25 2017 +0530
+++ b/mercurial/util.py	Fri Feb 10 16:56:29 2017 -0800
@@ -1097,7 +1097,7 @@
     return check
 
 # a whilelist of known filesystems where hardlink works reliably
-_hardlinkfswhitelist = set([
+_hardlinkfswhitelist = {
     'btrfs',
     'ext2',
     'ext3',
@@ -1109,7 +1109,7 @@
     'ufs',
     'xfs',
     'zfs',
-])
+}
 
 def copyfile(src, dest, hardlink=False, copystat=False, checkambig=False):
     '''copy a file, preserving mode and optionally other stat info like