--- a/mercurial/obsolete.py	Tue Oct 14 13:25:13 2014 -0700
+++ b/mercurial/obsolete.py	Tue Oct 14 13:26:01 2014 -0700
@@ -84,6 +84,7 @@
 # Options for obsolescence
 createmarkersopt = 'createmarkers'
 allowunstableopt = 'allowunstable'
+exchangeopt = 'exchange'
 
 ### obsolescence marker flag