Github Version Control

Matt Toegel matthew.toegel@njit.edu

Introduction

Getting Setup

  • Create an account or login to https://github.com

    • If it’s a new account, fill in the questionnaire

  • In the top right, click the + and choose "New Repository"

  • Name it [ucid]-[course]-[section] (i.e., mt85-IT000-000)

    • Check "Add a README file"

    • Leave "Add .gitignore" blank as we’ll create this later on

    • Click "Create Repository"

Don’t literally name it [ucid]-[course]-[section]
New Repository Creation Repository Configuration

Software

  • Check for git

    • In your terminal type git --version

      • If you get output you have git but may need to update

      • If you don’t get output, follow the steps based on your OS here

Create Your Key

  • An SSH key is a secure method of authenticating with GitHub. It consists of a private key (kept secure) and a public key (shared with GitHub)

    • We’ll need to create an SSH key (private/public key pair)

    • Upload the public key to GitHub (don’t upload to the repository)

You only need one SSH key per machine per Github account and never share your private key with anyone

  • Generate SSH key:

    • ssh-keygen -t ed25519 -C "your_github_email@example.com" (The C is uppercase)

    • Save it in your .ssh folder for consistency (follow the presented path in the parentheses and replace id_ed25519 with a more descriptive name, like github_key)

    • Optionally add a passphrase in the next step (will need to remake key if passphrase is forgotten)

sshkeygen

Get Your Key

  • Find your public key:

    • ls ~/.ssh

      • This will list the possible keys on your machine

  • Once found, output the content to the terminal

    • cat ~/.ssh/github-key.pub

      • Don’t forget the .pub at the end; you don’t want to mistakenly output the private key

    • The content should start with "ssh" and end with your email address (or whatever was used after -C in the previous step)

public key

Add to Github

  • Add the public key to Github:

    • Go to Settings > SSH and GPG Keys > New SSH Key

    • Name it to identify the machine

    • Paste your public key and save

new ssh key

Test by Cloning

  • Clone your repository:

    • Navigate to the directory for your class content

      • I generally put mine in a dedicated folder for the semester (i.e., NJIT/<semester>/<course>/)

    • Open Git Bash Here

    • Run git clone [SSH URL] (use SSH, not HTTPS)

New Repository Creation

  • This will likely fail, if it does, pay attention to the reason and proceed to the next steps

Adding Keys to the Key Ring

  • If SSH-Agent issues occurred:

    • Start ssh-agent: eval "$(ssh-agent -s)"

    • Add your private key: ssh-add ~/.ssh/github_key

      • Note it does not end with ".pub"

  • These commands add the private key to the current terminal session, if you close it you’ll need to rerun them

    • We’ll adjust something at the end to reduce these steps

  • Re-Run git clone [SSH URL] if it had failed previously (don’t rerun it if it had worked)

You’ll generally only need to clone your repo once per machine, refrain from repeatedly cloning as this will cause nested repositories and cause a lot of issues if not resolved.
This warning includes avoiding the usage of git init in the cloned repository directory.

All Set

  • Verify your setup (assuming the clone worked):

    • Navigate into your repository directory

      • Hint: cd <your_repo_name>

    • Run git status to see git-related output

Appendix: Tell Git Which Key To Use

  • Set a specific SSH key for a repository:

    • Navigate to your repository directory if you’re not there already

    • Edit .git/config via nano .git/config

    • Under [core]` add the following

      • sshCommand = "ssh -i ~/.ssh/github_key"

    • This configures Git to use the specified SSH key whenever it internally invokes the ssh command

      • -i tells it which identity to refer to

New Repository Creation

Alternatively you can use the following command to set the SSH key for the current repository:
git config core.sshCommand "ssh -i ~/.ssh/github_key"