diff -r 041f042afcc5 -r 827cb4fe62a3 mercurial/configitems.py
--- a/mercurial/configitems.py	Wed Sep 25 03:58:46 2019 +0200
+++ b/mercurial/configitems.py	Mon Sep 09 22:42:55 2019 +0200
@@ -733,6 +733,10 @@
 coreconfigitem('format', 'usestore',
     default=True,
 )
+coreconfigitem('format', 'use-side-data',
+    default=False,
+    experimental=True,
+)
 coreconfigitem('format', 'internal-phase',
     default=False,
     experimental=True,