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

builtin/clean.c

@@ -1009,6 +1009,9 @@ int cmd_clean(int argc, const char **argv, const char *prefix)
 		dir.flags |= DIR_KEEP_UNTRACKED_CONTENTS;
 	}
 
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+
 	if (read_cache() < 0)
 		die(_("index file corrupt"));