In b3025e3fe I had written that when following my recipe, the repository
remains in cherry-picking mode afterwards. In issue #516 I was told that
Repository.state_cleanup() is needed to correct that. Therefore add it
to the recipe.
Also add a note near the documentation for cherry-pick, so that nobody
will overlook this again. Apparently there are other times when you need
to do Repository.state_cleanup() as well, but it's not documented, I
don't know when and I don't want to take the time and find out. So leave
it at that for now.