I notice you don’t export the GIT_SSH_COMMAND variable, so it’s not actually available to the subsequent git command. That’s probably the issue.

However, before you continue, I see a number of things there that practically yell really bad idea. ⚠️

• You’re running Git as root. Git doesn’t do anything that needs root access, and running anything as root unnecessarily is an unnecessary security risk.
• You disable the SSH known hosts file and host key checking. This means that anyone who can mess with your network traffic can make you connect to anywhere they want, and have your Git command download whatever they want.
• I assume that if you clone in root, you intend to use the repository as root. In combination with not checking the identity of the remote host that makes it really easy for an attacker to get remote code execution.

Get GitHub's SSH key fingerprints - GitHub Docs, retrieve the keys, verify, and add them to the right user’s known hosts file, and use that file when connecting.

Don’t clone as root, clone as a regular user. If your tool really needs to run (or install) as root you can still do that after. Good luck! 🙂