diff -r 1ce46f0ee218 -r 604c086ddde6 mercurial/configitems.py
--- a/mercurial/configitems.py	Tue May 14 09:13:39 2019 -0700
+++ b/mercurial/configitems.py	Wed May 01 09:34:47 2019 -0700
@@ -529,6 +529,9 @@
 coreconfigitem('experimental', 'evolution.bundle-obsmarker',
     default=False,
 )
+coreconfigitem('experimental', 'log.topo',
+    default=False,
+)
 coreconfigitem('experimental', 'evolution.report-instabilities',
     default=True,
 )