mercurial/configitems.py

--- a/mercurial/configitems.py	Sun Oct 06 23:36:51 2019 -0400
+++ b/mercurial/configitems.py	Sun Oct 06 23:36:51 2019 -0400
@@ -748,6 +748,12 @@
     b'format', b'usestore', default=True,
 )
 coreconfigitem(
+    b'format',
+    b'exp-use-copies-side-data-changeset',
+    default=False,
+    experimental=True,
+)
+coreconfigitem(
     b'format', b'use-side-data', default=False, experimental=True,
 )
 coreconfigitem(