pack-bitmap.c: compute disk-usage with incremental MIDXs

In a similar fashion as previous commits, use nth_midxed_pack() instead
of accessing the MIDX's ->packs array directly to support incremental
MIDXs.

Signed-off-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ttaylorr

pack-bitmap.c

@@ -1774,7 +1774,7 @@ static unsigned long get_size_by_pos(struct bitmap_index *bitmap_git,
 			uint32_t midx_pos = pack_pos_to_midx(bitmap_git->midx, pos);
 			uint32_t pack_id = nth_midxed_pack_int_id(bitmap_git->midx, midx_pos);
 
-			pack = bitmap_git->midx->packs[pack_id];
+			pack = nth_midxed_pack(bitmap_git->midx, pack_id);
 			ofs = nth_midxed_offset(bitmap_git->midx, midx_pos);
 		} else {
 			pack = bitmap_git->pack;
@@ -3021,7 +3021,7 @@ static off_t get_disk_usage_for_type(struct bitmap_index *bitmap_git,
 				off_t offset = nth_midxed_offset(bitmap_git->midx, midx_pos);
 
 				uint32_t pack_id = nth_midxed_pack_int_id(bitmap_git->midx, midx_pos);
-				struct packed_git *pack = bitmap_git->midx->packs[pack_id];
+				struct packed_git *pack = nth_midxed_pack(bitmap_git->midx, pack_id);
 
 				if (offset_to_pack_pos(pack, offset, &pack_pos) < 0) {
 					struct object_id oid;