Set up Git Authentication (on the command line)

You're here because you'd like to know how to set up git authentication (on the command line).

What does this mean? It means you probably just got an error like this:

      $ git push -u origin main
          Username for 'https://github.com': arteen1000
          Password for 'https://arteen1000@github.com': 
          remote: Support for password authentication was
          removed on August 13, 2021.
          ...
          fatal: Authentication failed for ...
    

Here are the steps to fix this (and never have to type your password or username again):

• First, check for existing ssh keys. This is as simple as checking if ~/.ssh has any files starting with id_ (by default, they are named by that convention). If you do not have an ssh key, then simply run ssh-keygen -t ed25519 -C 'name@email.com' and press <RET> at every prompt. Ideally, you'd use the same email as your GitHub account, replacing name@email.com.
• You should now have a public/private key-pair inside ~/.ssh. For me, the keys are at ~/.ssh/id_ed25519 and ~/.ssh/id_ed25519.pub, where the one ending with .pub is my public key.
• Now type emacs ~/.ssh/config. Make sure you install emacs at this step if you don't already have it, unless you want to resort to a more inferior text editor.
• Type the following into your configuration:

            Host github.com
              AddKeysToAgent yes
              IdentityFile ~/.ssh/id_ed25519
          

  You can replace ~/.ssh/id_ed25519 as necessary with the corresponding private key.
• Copy the contents of your public key (~/.ssh/id_ed25519.pub) to your clipboard and navigate to GitHub -> Profile (top right) -> Settings -> SSH and GPG keys. Click on New SSH Key, give it a descriptive title, and paste the contents of your public key into the Key field. Click Add SSH key.
• Verify the connection using ssh -T git@github.com, typing yes at the prompt.
• Make sure that you are using SSH for the remote URL (as opposed to HTTPS). If you are not, you can change the remote for your repository to do so using git remote set-url origin 'git@github.com:user/repository.git'. Replace git@github.com:user/repository.git as necessary.
• Finally, we reap the fruits of our labor. You can now do git push -u origin main to push your main branch to GitHub. Congratulations.