Re: "Not possible to fast-forward" when pull.ff=only and new commits on remote

> > Running a sequence of traversals like this can be slow, because we may
> > walk over the same history again and again. But I think in the usual
> > non-octopus cases we'd only have one entry, so we'd only be adding a
> > single extra merge-base traversal in most cases.
> >
> > It does feel like this could be combined with get_can_ff() somehow so
> > that we're not adding even that single traversal. But I expect that may
> > be hard to do because of the multiple heads (e.g., we cannot use the
> > usual ahead/behind code).
> 
> I'd leave such an optimization as a separate topic.  This was meant
> to be a regression fix.