Merge branch 'ds/add-rm-with-sparse-index'

Merge branch 'ds/add-rm-with-sparse-index'

"git add", "git mv", and "git rm" have been adjusted to avoid
updating paths outside of the sparse-checkout definition unless
the user specifies a "--sparse" option.

* ds/add-rm-with-sparse-index:
  advice: update message to suggest '--sparse'
  mv: refuse to move sparse paths
  rm: skip sparse paths with missing SKIP_WORKTREE
  rm: add --sparse option
  add: update --renormalize to skip sparse paths
  add: update --chmod to skip sparse paths
  add: implement the --sparse option
  add: skip tracked paths outside sparse-checkout cone
  add: fail when adding an untracked sparse file
  dir: fix pattern matching on dirs
  dir: select directories correctly
  t1092: behavior for adding sparse files
  t3705: test that 'sparse_entry' is unstaged