changegroup: add `delta_base_reuse_policy` argument The argument available through function from changegroup.apply to `revlog.apply` allow to override the revlog configuration in terms of delta-base-reuse policy when searching for a delta to store a revision. It will be put to use in the next changesets.

bundleoperation: optionnaly record the `remote` that produced the bundle We have the information at hand, and the peer now have knownledge of its `path` object, which constaints useful behavior configuration. So the simpler seems to be to pass that object around so it can be used if needed.

delta-find: add a test checking various simple behavior There are enough work happening in this area that it is worth having a dedicated test for it. So far we add to small test checking that the "best" parent is picked as the delta base and that this behavior can be controlled during commit and unbundle.