I've updated the pull-request to list directories pointed to by listed symbolic links, preventing cyclic listing. An extra instance method `pathlib.Path._iterdir_recursive` was added for this.

We still need to decide whether to yield the directories themselves rather than just the files under those directories. Very easy to implement this.

One thing I just realised is that a symlink can point to a subdirectory further down the chain. The current implementation will list the files under that directory using the symlink as prefix rather than the full path. Shouldn't matter though.