> > @@ -3807,6 +3807,7 @@ static int stdin_packs_hints_nr;
> >  struct stdin_packs_context {
> >  	struct rev_info *revs;
> >  	enum stdin_packs_mode mode;
> > +	struct oid_array extra_roots;
>
> I believe this should be an oidset to avoid adding duplicate objects
> that appear multiple times. The order of these extra roots doesn't
> matter (such as in a --topo-order walk). We only care about the
> binary "reachable or not?" question.