When there are too many packfiles in a repository (which is not
recommended), looking up an object in these would require
consulting many pack .idx files; a new mechanism to have a single
file that consolidates all of these .idx files is introduced.
* ds/multi-pack-index: (32 commits)
pack-objects: consider packs in multi-pack-index
midx: test a few commands that use get_all_packs
treewide: use get_all_packs
packfile: add all_packs list
midx: fix bug that skips midx with alternates
midx: stop reporting garbage
midx: mark bad packed objects
multi-pack-index: store local property
multi-pack-index: provide more helpful usage info
midx: clear midx on repack
packfile: skip loading index if in multi-pack-index
midx: prevent duplicate packfile loads
midx: use midx in approximate_object_count
midx: use existing midx when writing new one
midx: use midx in abbreviation calculations
midx: read objects from multi-pack-index
config: create core.multiPackIndex setting
midx: write object offsets
midx: write object id fanout chunk
midx: write object ids in a chunk
...