setdiscover: allow to ignore part of the local graph...
setdiscover: allow to ignore part of the local graph
Currently, the push discovery first determines the full set of common nodes
before looking into what changesets are outgoing. When pushing a specific
subset, this can lead to pathological situations where we search for the status
of thousand of local heads that are unrelated to the requested pushes.
To fix this, we need to teach the discovery to ignores part of the graph. Most
of the necessary pieces were already in place. This changeset just makes them
available to higher level API and tests them.
Change actually impacting pushes are coming in a later changeset.
