diff -r c2b30348930f -r 37450a122128 mercurial/configitems.py
--- a/mercurial/configitems.py	Fri Oct 20 05:53:35 2017 -0700
+++ b/mercurial/configitems.py	Tue Oct 24 11:14:38 2017 -0700
@@ -578,6 +578,9 @@
 coreconfigitem('merge', 'checkignored',
     default='abort',
 )
+coreconfigitem('experimental', 'merge.checkpathconflicts',
+    default=True,
+)
 coreconfigitem('merge', 'followcopies',
     default=True,
 )