Re: [PATCH v2 6/8] repack: track the preferred pack explicitly in MIDX write steps

> A MIDX write step marks preferred packs in its string-list entries and
> chooses the last marked entry when executing the step. That makes the
> choice depend on list order, preventing the list from being sorted for
> membership checks.
> 
> Record the last candidate directly in the step, borrowing its name from
> the write list. This preserves preferred-pack selection while allowing
> the list to be sorted without changing that choice.

> @@ -719,7 +713,7 @@ static int repack_make_midx_compaction_plan(struct repack_write_midx_opts *opts,
>  
>  		item = string_list_append(&step.u.write, buf.buf);
>  		if (p->multi_pack_index || i == opts->geometry->pack_nr - 1)
> -			item->util = (void *)1; /* mark as preferred */
> +			step.preferred_pack = item->string;