diff -r 12966768595a -r 62f325f9b347 mercurial/configitems.py
--- a/mercurial/configitems.py	Thu Sep 23 09:42:20 2021 -0700
+++ b/mercurial/configitems.py	Wed Sep 22 17:14:54 2021 -0400
@@ -207,6 +207,11 @@
     b'pushing',
     default=list,
 )
+coreconfigitem(
+    b'bookmarks',
+    b'mirror',
+    default=False,
+)
 # bundle.mainreporoot: internal hack for bundlerepo
 coreconfigitem(
     b'bundle',