--- a/mercurial/configitems.py	Wed Jul 05 00:01:30 2017 +0200
+++ b/mercurial/configitems.py	Fri Jun 30 03:42:20 2017 +0200
@@ -104,6 +104,9 @@
 coreconfigitem('devel', 'strip-obsmarkers',
     default=True,
 )
+coreconfigitem('format', 'aggressivemergedeltas',
+    default=False,
+)
 coreconfigitem('hostsecurity', 'ciphers',
     default=None,
 )