diff -r aacb17cc0ee4 -r bed1d2eaa108 mercurial/configitems.py
--- a/mercurial/configitems.py	Sun Oct 08 21:47:14 2017 +0200
+++ b/mercurial/configitems.py	Sun Oct 08 21:48:40 2017 +0200
@@ -344,6 +344,12 @@
 coreconfigitem('http_proxy', 'user',
     default=None,
 )
+coreconfigitem('merge', 'checkunknown',
+    default='abort',
+)
+coreconfigitem('merge', 'checkignored',
+    default='abort',
+)
 coreconfigitem('merge', 'followcopies',
     default=True,
 )