Upload pack: We have to wait for the client to close the connection by itself.

Most versions of Git freakout if we close the connection ourselves,
and will not create an empty repository on clone.

dulwich/server.py

@@ -411,10 +411,6 @@ class ProtocolGraphWalker(object):
         :param heads: a dict of refname->SHA1 to advertise
         :return: a list of SHA1s requested by the client
         """
-        if not heads:
-            # The repo is empty, so short-circuit the whole process.
-            self.proto.write_pkt_line(None)
-            return []
         values = set(heads.itervalues())
         if self.advertise_refs or not self.http_req:
             for i, (ref, sha) in enumerate(sorted(heads.iteritems())):