--- a/mercurial/interfaces/repository.py	Thu Apr 08 16:30:10 2021 +0200
+++ b/mercurial/interfaces/repository.py	Mon Apr 19 11:22:21 2021 +0200
@@ -1856,7 +1856,9 @@
     def savecommitmessage(text):
         pass
 
-    def register_sidedata_computer(kind, category, keys, computer, flags):
+    def register_sidedata_computer(
+        kind, category, keys, computer, flags, replace=False
+    ):
         pass
 
     def register_wanted_sidedata(category):