Re: [PATCH v3 1/2] pack-bitmap.c: remove unnecessary "open_pack_index()" calls

> Yeah, I agree that 1k is a lot more compelling. The big impractical
> thing I think is that if the bitmapped pack is older (and it usually
> is), then we'd often open all the other packs anyway:
>
>   - if the start of the traversal is in the bitmapped pack, then we
>     fruitlessly open each of the others looking for the object (since
>     the bitmapped one will come last in the reverse-chronological
>     sorting)
>
>   - if it isn't in the bitmapped pack, then we'll end up opening all
>     those other packs anyway to fill out the bitmap (since by definition
>     it can't be included in the on-disk bitmaps)
>
> So I'd be surprised if it ever mattered in the real world. Though again,
> I think the new code is less surprising in general, and could matter if
> we changed other things (e.g., if we prioritized lookups in a pack with
> a .bitmap).