Merge branch 'jh/notes-merge-in-git-dir-worktree' into maint

Running "notes merge --commit" failed to perform correctly when run from any directory inside $GIT_DIR/. When "notes merge" stops with conflicts, $GIT_DIR/NOTES_MERGE_WORKTREE is the place a user edits to resolve it. By Johan Herland (3) and Junio C Hamano (1) * jh/notes-merge-in-git-dir-worktree: notes-merge: Don't remove .git/NOTES_MERGE_WORKTREE; it may be the user's cwd notes-merge: use opendir/readdir instead of using read_directory() t3310: illustrate failure to "notes merge --commit" inside $GIT_DIR/ remove_dir_recursively(): Add flag for skipping removal of toplevel dir