--- a/mercurial/configitems.py	Mon Oct 09 15:13:41 2017 +0200
+++ b/mercurial/configitems.py	Tue Oct 10 17:50:27 2017 +0200
@@ -411,6 +411,12 @@
 coreconfigitem('experimental', 'spacemovesdown',
     default=False,
 )
+coreconfigitem('experimental', 'sparse-read',
+    default=False,
+)
+coreconfigitem('experimental', 'sparse-read.density-threshold',
+    default=0.25,
+)
 coreconfigitem('experimental', 'treemanifest',
     default=False,
 )