--- a/mercurial/configitems.py	Thu Jul 19 10:06:58 2018 +0200
+++ b/mercurial/configitems.py	Thu Jul 19 10:35:29 2018 +0200
@@ -637,9 +637,6 @@
     default=None,
     generic=True,
 )
-coreconfigitem('format', 'aggressivemergedeltas',
-    default=True,
-)
 coreconfigitem('format', 'chunkcachesize',
     default=None,
 )
@@ -930,6 +927,10 @@
 coreconfigitem('push', 'pushvars.server',
     default=False,
 )
+coreconfigitem('revlog', 'optimize-delta-parent-choice',
+    default=True,
+    # formely an experimental option: format.aggressivemergedeltas
+)
 coreconfigitem('server', 'bookmarks-pushkey-compat',
     default=True,
 )