Adds a new discovery method based on repeatedly sampling the still
undecided subset of the local node graph to determine the set of nodes
common to both the client and the server.
For small differences between client and server, it uses about the same
or slightly fewer roundtrips than the old tree-based discovery. For
larger differences, it typically reduces the number of roundtrips
drastically (from 150 to 4, for instance).
The old discovery code now lives in treediscovery.py, the new code is
in setdiscovery.py.
Still missing is a hook for extensions to contribute nodes to the
initial sample. For instance, Augie's remotebranches could contribute
the last known state of the server's heads.
Credits for the actual sampler and computing common heads instead of
bases go to Benoit Boissinot.
We don't support passwords in ssh URLs, and neither do some versions
of Python's urllib. Since we don't actually care much here, punt with
a glob in the test.
This is a simple patch to make hg push/hg outgoing print their remote target
path even if the operation fails. I'm not sure if the original behavior was by
design.
This patch also changes one test to reflect the changed behaviour.
