The client MUST write all obj-ids which it only has shallow copies
of (meaning that it does not have the parents of a commit) as
'shallow' lines so that the server is aware of the limitations of
-the client's history. Clients MUST NOT mention an obj-id which
-it does not know exists on the server.
+the client's history.
The client now sends the maximum commit history depth it wants for
this transaction, which is the number of commits it wants from the