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+There are two Pack push-pull protocols.
+
+upload-pack (S) | fetch/clone-pack (C) protocol:
+
+	# Tell the puller what commits we have and what their names are
+	S: SHA1 name
+	S: ...
+	S: SHA1 name
+	S: # flush -- it's your turn
+	# Tell the pusher what commits we want, and what we have
+	C: want name
+	C: ..
+	C: want name
+	C: have SHA1
+	C: have SHA1
+	C: ...
+	C: # flush -- occasionally ask "had enough?"
+	S: NAK
+	C: have SHA1
+	C: ...
+	C: have SHA1
+	S: ACK
+	C: done
+	S: XXXXXXX -- packfile contents.
+
+send-pack | receive-pack protocol.
+
+	# Tell the pusher what commits we have and what their names are
+	C: SHA1 name
+	C: ...
+	C: SHA1 name
+	C: # flush -- it's your turn
+	# Tell the puller what the pusher has
+	S: old-SHA1 new-SHA1 name
+	S: old-SHA1 new-SHA1 name
+	S: ...
+	S: # flush -- done with the list
+	S: XXXXXXX --- packfile contents.