--- a/mercurial/configitems.py	Thu Nov 16 03:52:38 2017 +0100
+++ b/mercurial/configitems.py	Thu Nov 16 03:52:42 2017 +0100
@@ -535,6 +535,9 @@
 coreconfigitem('experimental', 'revlogv2',
     default=None,
 )
+coreconfigitem('experimental', 'single-head-per-branch',
+    default=False,
+)
 coreconfigitem('experimental', 'spacemovesdown',
     default=False,
 )