I'm using esp32-s3 on micropython 1.19.1.

On mpremote document.
If you use cp -r, it assumes you can copy whole directory to esp32.

But when I use following command on Windows,
python -m mpremote cp -r main/ :

REPL give me an OSError:

cp main/d40.py :main/
Traceback (most recent call last):
  File "", line 1, in 
OSError: [Errno 21] EISDIR