If you are thinking of going down this route with this tool or another tool, don’t.
If you feel the need to add secrets to a git repository that means you have a problem with your development/deployment workflow.
Secrets shouldn’t live in product source code just like configuration shouldn’t live in product source code.
This, it is a very very bad idea.
Other arguments against it: - it opens the door to mistake, i.e. you crypt a bunch of file but easily forget about one. - git is often used in public forges. What is encrypted and not visible with common computing hardware now doesn't mean it will stay like this in the foreseeable future. You should consider any content or communications, you are transferring accross the internet as public as you can't control who is dumping what and when it will be decryptable.