send-pack related

I have a repo A ; AM is mirror of A.
I clone based on Mirror AM. However I would like Git to transparently
update A instead of AM
Solution I am using is pushurl. However I need to configure each client for it.

Is there a way I can configure AM in such way that I ship changes A.

I have tried following in pre-receive; didn't work as intended

git send-pack --all localhost:/home/mvaidya/playground/m2

Thank You
-Mahesh