How to get diff of a directory with batdiff?

In git, I have some modified file in a directory, then I can get all the diff of all the files.
```sh
git diff dir/
git diff .
```
But doesn't work with batdiff.
```
batdiff .
[bat error]: '.' is a directory.
```
Is it possible to achieve the same thing with batdiff?
Thanks in advance.