diff -r cf49e54ef965 -r 1c52d77d7861 mercurial/upgrade_utils/engine.py
--- a/mercurial/upgrade_utils/engine.py	Tue Apr 06 10:38:11 2021 +0200
+++ b/mercurial/upgrade_utils/engine.py	Tue Apr 06 10:38:27 2021 +0200
@@ -390,7 +390,7 @@
     are cloned"""
     for path, kind, st in sorted(srcrepo.store.vfs.readdir(b'', stat=True)):
         # don't copy revlogs as they are already cloned
-        if path.endswith((b'.i', b'.d', b'.n', b'.nd')):
+        if store.revlog_type(path) is not None:
             continue
         # Skip transaction related files.
         if path.startswith(b'undo'):