--- a/mercurial/configitems.py	Fri Jun 30 03:46:00 2017 +0200
+++ b/mercurial/configitems.py	Fri Jun 30 03:46:01 2017 +0200
@@ -164,3 +164,6 @@
 coreconfigitem('worker', 'backgroundclosethreadcount',
     default=4,
 )
+coreconfigitem('worker', 'numcpus',
+    default=None,
+)