diff -r c08ea1e219c0 -r e90130af47ce mercurial/configitems.py
--- a/mercurial/configitems.py	Thu Jul 19 21:36:24 2018 +0900
+++ b/mercurial/configitems.py	Thu Jul 19 11:10:48 2018 -0700
@@ -929,7 +929,7 @@
 )
 coreconfigitem('revlog', 'optimize-delta-parent-choice',
     default=True,
-    # formely an experimental option: format.aggressivemergedeltas
+    alias=[('format', 'aggressivemergedeltas')],
 )
 coreconfigitem('server', 'bookmarks-pushkey-compat',
     default=True,