diff -r 498697fe41f2 -r 645b6684cf5b mercurial/configitems.py
--- a/mercurial/configitems.py	Thu Oct 19 21:50:14 2017 +0200
+++ b/mercurial/configitems.py	Fri Oct 20 22:25:09 2017 +0900
@@ -314,6 +314,9 @@
 coreconfigitem('email', 'reply-to',
     default=None,
 )
+coreconfigitem('email', 'to',
+    default=None,
+)
 coreconfigitem('experimental', 'archivemetatemplate',
     default=dynamicdefault,
 )