setdiscovery: directly run '_updatesample' The heads and exponential sample are going to end up in the same set before any extra processing happens. We simplify the code by directly updating a set with heads. Changes in the order the set is built lead to small changes in the random sampling output. But after double checking, I can confirm the input data to the random sampling is consistent.

--- a/mercurial/setdiscovery.py	Wed Jan 07 17:17:56 2015 -0800
+++ b/mercurial/setdiscovery.py	Wed Jan 07 17:23:21 2015 -0800
@@ -108,7 +108,7 @@
     always = dag.headsetofconnecteds(nodes)
     if size <= len(always):
         return always
-    sample = set()
+    sample = always
     # update from heads
     _updatesample(dag, nodes, sample, always)
     # update from roots