rewind: update the working copy if it gets obsoleted If the working copy parent is rewinded, follow the rewind.

rewind: add a message about obsolete changeset Not the best output, but useful to have the data. We can improve that later.

rewind: obsolete latest successors unless instructed otherwise To prevent the creations of divergence, we automatically mark the successors set of the rewinded changeset as obsoleted by the rewind result. A new flag `--as-divergence` is added to disable this behavior.