Github Version Control

Introduction

This lesson will cover how to set up GitHub for your course
This assumes you’ve gone through the following lesson:
- Basic Command Line Interface (CLI)

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"

Important

Don’t literally name it [ucid]-[course]-[section]

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)

Note	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)

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)

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

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)

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)

Important

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

Tip	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"`