diff -r 47719d7c581f -r 4265bfb53dd3 mercurial/configitems.py
--- a/mercurial/configitems.py	Tue Dec 04 17:04:19 2018 -0500
+++ b/mercurial/configitems.py	Sun Dec 09 23:48:50 2018 -0500
@@ -1274,6 +1274,9 @@
 coreconfigitem('web', 'cache',
     default=True,
 )
+coreconfigitem('web', 'comparisoncontext',
+    default=5,
+)
 coreconfigitem('web', 'contact',
     default=None,
 )