Fixes for push corner case TAH found a bug where push would push things the remote already had, raising an assertion. This turned out to be because the changeset protocol was not recording a common subset node in one case. Also discovered was that the protocol was queueing multiple copies of a node for pull. Fixed by changing fetch to a hash. Add some more debugging output.

#header#
# HG changeset patch
# User #author#
# Date #date|date#
# Node ID #node#
#parent#
#desc#

#diff#