Merge branch 'en/sparse-checkout'

"sparse-checkout" UI improvements. * en/sparse-checkout: sparse-checkout: provide a new reapply subcommand unpack-trees: failure to set SKIP_WORKTREE bits always just a warning unpack-trees: provide warnings on sparse updates for unmerged paths too unpack-trees: make sparse path messages sound like warnings unpack-trees: split display_error_msgs() into two unpack-trees: rename ERROR_* fields meant for warnings to WARNING_* unpack-trees: move ERROR_WOULD_LOSE_SUBMODULE earlier sparse-checkout: use improved unpack_trees porcelain messages sparse-checkout: use new update_sparsity() function unpack-trees: add a new update_sparsity() function unpack-trees: pull sparse-checkout pattern reading into a new function unpack-trees: do not mark a dirty path with SKIP_WORKTREE unpack-trees: allow check_updates() to work on a different index t1091: make some tests a little more defensive against failures unpack-trees: simplify pattern_list freeing unpack-trees: simplify verify_absent_sparse() unpack-trees: remove unused error type unpack-trees: fix minor typo in comment