rename of a folder to any subdirectory of itself should be prevented

[flokaiser]

Hi :D
littlefs currently does not catch when a folder is moved to one of its sub-directories.
This leads to the directory being moved to just disappear.
If I understand this correctly that means in the following example all storage taken up by a file with the path /a/b/file.bin will never be freed after a rename("/a/b", "/a/b/c/d")
I have attached a simple script that describes the issue better than I could in text :)

Thanks!

littlefs_rename_bug.py

[geky]

That's certainly a funny bug.

I'm surprised no one else ran into it until now, but I guess it is a rather strange operation to attempt.

Unfortunately, detecting this condition is surprisingly tricky and would require some internal changes, so I think this will be a "wontfix" item until littlefs3.