Merge branch 'vd/sparse-clean-etc'

"git update-index", "git checkout-index", and "git clean" are taught to work better with the sparse checkout feature. * vd/sparse-clean-etc: update-index: reduce scope of index expansion in do_reupdate update-index: integrate with sparse index update-index: add tests for sparse-checkout compatibility checkout-index: integrate with sparse index checkout-index: add --ignore-skip-worktree-bits option checkout-index: expand sparse checkout compatibility tests clean: integrate with sparse index reset: reorder wildcard pathspec conditions reset: fix validation in sparse index test