Re: [PATCH 38/49] builtin/repack.c: inline packs within `write_midx_included_packs()`

> The logic for computing which packs are supposed to appear in the
> resulting MIDX is within `midx_included_packs()`, where it is aware of
> details like which cruft pack(s) were written/combined, if/how we did a
> geometric repack, etc.
> 
> Computing this list ourselves before providing it to the sole function
> to make use of that list `write_midx_included_packs()` is somewhat
> awkward. In the future, repack will learn how to write incremental
> MIDXs, which will use a very different pack selection routine.
> 
> Instead of doing something like:
> 
>     struct string_list included_packs = STRING_LIST_INIT_DUP;
>     if (incremental) {
>         midx_incremental_included_packs(&included_packs, ...):
>         write_midx_incremental_included_packs(&included_packs, ...);
>     } else {
>         midx_included_packs(&included_packs, ...):
>         write_midx_included_packs(&included_packs, ...);
>     }
> 
> in the future, let's have each function which writes a MIDX be
> responsible for itself computing the list of included packs. Inline the
> declaration and initialization of `included_packs` into the
> `write_midx_included_packs()` function itself, and repeat that pattern
> in the future when we introduce new ways to write MIDXs.