Generating a new SSH key and adding it to the ssh-agent - GitHub Docs
https://docs.github.com/en/free-pro-team@latest/github/authenticating-to-github/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent
// ここ見て今さら知ったんだけどさ、今って rsa とかじゃなく Ed25519 なんね。