--- a/hgext/git/manifest.py	Mon Sep 07 15:46:56 2020 -0400
+++ b/hgext/git/manifest.py	Mon Sep 07 16:13:10 2020 -0400
@@ -217,7 +217,9 @@
             return b''
 
     def copy(self):
-        pass
+        return gittreemanifest(
+            self._git_repo, self._tree, dict(self._pending_changes)
+        )
 
     def items(self):
         for f in self: