Merge branch 'ds/commit-and-checkout-with-sparse-index'

"git checkout" and "git commit" learn to work without unnecessarily expanding sparse indexes. * ds/commit-and-checkout-with-sparse-index: unpack-trees: resolve sparse-directory/file conflicts t1092: document bad 'git checkout' behavior checkout: stop expanding sparse indexes sparse-index: recompute cache-tree commit: integrate with sparse-index p2000: compress repo names p2000: add 'git checkout -' test and decrease depth