Re: Add "--show-all" revision walker flag for debugging

> I, too, have some reservations about adding any kind of generation 
> header to commit objects.  First because it can be generated and 
> maintained locally, just like the pack index.  But also because its 
> usefulness has not been proven in all possible graph topologies, and 
> adding it to the commit header pretty much deny any further 
> modifications/improvements on it, if for example some other kind of 
> generation notation becomes advantageous to use.