Make `git add --patch` work on encrypted files?

I have a large encrypted file which, when changed, is easier to review and commit using `git add -p`.

However, when I run a `git add --patch` on such a file, I get a `Only binary files changed.` message from git. I can see from the Git docs that the `textconv` option might not be used here.

Would it be possible to add support for this in `git-crypt` ?

Failing which, is there a workaround that I can do in my `.gitconfig` that can resolve this issue?

Thanks!