Merge branch 'ds/status-with-sparse-index'

Merge branch 'ds/status-with-sparse-index'

"git status" codepath learned to work with sparsely populated index
without hydrating it fully.

* ds/status-with-sparse-index:
  t1092: document bad sparse-checkout behavior
  fsmonitor: integrate with sparse index
  wt-status: expand added sparse directory entries
  status: use sparse-index throughout
  status: skip sparse-checkout percentage with sparse-index
  diff-lib: handle index diffs with sparse dirs
  dir.c: accept a directory as part of cone-mode patterns
  unpack-trees: unpack sparse directory entries
  unpack-trees: rename unpack_nondirectories()
  unpack-trees: compare sparse directories correctly
  unpack-trees: preserve cache_bottom
  t1092: add tests for status/add and sparse files
  t1092: expand repository data shape
  t1092: replace incorrect 'echo' with 'cat'
  sparse-index: include EXTENDED flag when expanding
  sparse-index: skip indexes with unmerged entries