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.
merge: warning: conflicts during merge
merging a
merging a failed!
32e80765d7fe+75234512624c+ tip
something else
=======
something
M a