diff -r bed1d2eaa108 -r 486dbd6afa57 mercurial/configitems.py
--- a/mercurial/configitems.py	Sun Oct 08 21:48:40 2017 +0200
+++ b/mercurial/configitems.py	Sun Oct 08 21:41:10 2017 +0200
@@ -146,6 +146,9 @@
 coreconfigitem('devel', 'strip-obsmarkers',
     default=True,
 )
+coreconfigitem('devel', 'warn-config',
+    default=None,
+)
 coreconfigitem('diff', 'nodates',
     default=None,
 )