--- a/mercurial/hook.py	Tue Nov 03 17:13:27 2015 -0800
+++ b/mercurial/hook.py	Fri Nov 06 11:08:11 2015 -0500
@@ -122,8 +122,7 @@
     # make in-memory changes visible to external process
     tr = repo.currenttransaction()
     repo.dirstate.write(tr)
-    if tr:
-        tr.writepending()
+    if tr and tr.writepending():
         env['HG_PENDING'] = repo.root
 
     for k, v in args.iteritems():