Merge branch 'vd/sparse-reset' into ld/sparse-diff-blame

* vd/sparse-reset: unpack-trees: improve performance of next_cache_entry reset: make --mixed sparse-aware reset: make sparse-aware (except --mixed) reset: integrate with sparse index reset: expand test coverage for sparse checkouts sparse-index: update command for expand/collapse test reset: preserve skip-worktree bit in mixed reset reset: rename is_missing to !is_in_reset_tree