Maybe credential.helper or the old Fine-grained Personal Access Token (FGPAT) is tricking you.

IT IS SO WEIRD AND FRUSTRATING!!!

My old FGPAT is still valid till now. I used it to clone my private repo about 1 month ago. It works fine then.

Today, I deleted the repo folder and wanna clone again, using git clone https://oauth2:$GITHUB_API_KEY@github.com/MY_USERNAME/MY_PRIVATE_REPO.git, error:

git clone https://oauth2:$GITHUB_API_KEY@github.com/MY_USERNAME/MY_PRIVATE_REPO.git
Cloning into 'MY_PRIVATE_REPO'...
remote: Support for password authentication was removed on August 13, 2021.
remote: Please see https://docs.github.com/get-started/getting-started-with-git/about-remote-repositories#cloning-with-https-urls for information on currently recommended modes of authentication.
fatal: Authentication failed for 'https://github.com/MY_USERNAME/MY_PRIVATE_REPO.git/'

This error made me believe that the problem is the authentication method "password authentication".

So I open the link and read, nothing helps. I googled all kinds of articles and posts to figure this out, found out some HTTPS URL formats, none of them work:

git clone https://$GITHUB_API_KEY@github.com/MY_USERNAME/MY_PRIVATE_REPO.git
git clone https://MY_USERNAME:$GITHUB_API_KEY@github.com/MY_USERNAME/MY_PRIVATE_REPO.git
git clone https://github.com/MY_USERNAME/MY_PRIVATE_REPO.git

After hours of frustration, I did sudo git config --system --unset credential.helper, then https://oauth2:$GITHUB_API_KEY@github.com/MY_USERNAME/MY_PRIVATE_REPO.git, still get the same error.

I created a new FGPAT, solved.

Conclusion

It seems that a new FGPAT helps, but sudo git config --system --unset credential.helper is still worth a try.

I still can not understand why should I create a new FGPAT while the old one is still valid.

Github | Encounter "Support for password authentication was removed on August 13, 2021." error

Conclusion