Merge branch 'js/update-index-ignore-removal-for-skip-worktree'

"git stash save" in a working tree that is sparsely checked out mistakenly removed paths that are outside the area of interest. * js/update-index-ignore-removal-for-skip-worktree: stash: handle staged changes in skip-worktree files correctly update-index: optionally leave skip-worktree entries alone