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.
Content-type: text/xml
<rss version="2.0">
<channel>
<link>#url#</link>
<language>en-us</language>