Intro to Git & GitHub
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Intro to Git

Learning Objectives

  • Define version control and identify what problems it solves for developers
  • Define a repository (aka repo) and identify the parts of a repo
  • Differentiate between a local repository and a remote repository
  • Synchronize a local repository with a remote repository using git with Github
  • Describe forking and making a pull request

Framing (5 min / 0:05)

Git is one of a couple tools that you will end up using every day as a developer; it's an essential component to every developer's work. So what is it?

Git is a version control tool: it keeps track of changes across a collection of files for us. When we use Git, we can see what changes we made and seamlessly merge them with changes from our coworkers.

Version Control (20 min / 0:25)

Simply put, version control is a way of tracking changes made to a file or group of files over time.

Git is a version control system. There are others, like Mercurial and SVN, but Git is the most popular and the most powerful. Git will track changes made to a group of files in a directory. Git users like ourselves can commit or save our changes and have access to a history of all the saves or commits that we have made.

Think, Pair, Share

5 min exercise, 5 min review

Turn to the person next to you and discuss the questions below. After 5 minutes, we'll go over responses as a class.

  • Why might we want to have different versions of a file?
  • What strategies have you used to keep track of changes you've made to a document or file before? If you haven't, brainstorm ways you might keep track of different versions of a file/document.
  • How well did that strategy work? Was it painful? Can you see any limitations or problems associated with that strategy?
  • How might that approach work in a team environment?

Follow Up

If you've worked with track changes in Microsoft Word, then you're familiar with part of what Git does. Track changes will track any changes (inserted text, deleted text, etc) to a document. Git can show differences between the current version and the previous version in something called a diff (command: git diff). A diff will show what has been added in green text or highlighting, while displaying the things removed in red.

Git does this and a lot more. For example, if you and your coworker are writing a memo in Microsoft Word and using track changes, how do you keep track of which version is the final version (yours or your coworker's)? One common solution to this is to make a copy of the memo and add your initials to the file name, along with the date and time so you can keep track of different versions of the memo. Someone then has to manually add any changes you make to their version, or vice versa.

Imagine if we had to do something like that with a codebase. The codebase for even a simple web application can be many files - it would take forever and be extremely error prone!

This is the problem Git solves for developers.

Here's a short list of things you can do with Git:

  • track changes to a set of files over time (version control)
  • save your work with descriptive save messages (commits)
  • track multiple versions and histories of the same codebase (branching)

How To Work with Git (10 min / 0:35)

The basics of working with Git could be somewhat familiar to you. Git works inside of a repository: a folder where Git is watching and tracking changes to files. When we want to record or commit some changes we've made and 'save our progress so far, we do so by staging those changes and then committing them.

A repository is like a special kind of filing cabinet that stores a bunch of snapshots of a project taken at different points the project's development. It contains all of a project's branches, each of which are composed of commits representing individual changes to a project over time. As such, a repository encompasses all of the different versions of a project and their development histories.

"Saving" our work with Git involves two steps: staging some changes and the committing them. Each commit is like a "save-point" that, collectively, track the version of our project at a given point in time. Each commit has a commit message that describes the changes made to a file or group of files. Commits get stored together in a repository.

For every feature you add, even a very small one, you should make a commit. If you go an hour without committing, it's usually best to go ahead and commit what you have gotten to work in the last hour. Your mileage may vary, but it's probably best to commit ever 20-45 minutes.

Commit Early, Commit Often!

At any given time, we can go back to the version of our project at any given commit. This ability gives us a lot of room to experiment. It's absolutely essential to have this kind of safety net as a developer!

When collaborating on a project with other developers, Git gives us tools to create our own "area" for writing code, within that project. This "area" is called a branch. A branch is a sequence of commits that represents a version of our project. All Git repositories start with at least one branch (master).

Exercise 1: Creating a Repository and Committing - We Do (5 min / 0:40)

  1. Create a new sample_portfolio folder in your sandbox directory.
  2. Change your working directory to sample_portfolio.
  3. Initialize a git repository in the sample_portfolio folder. (git init)
  4. Create a index.html file and write anything in it.
  5. Add index.html to the staging area and then make a commit.

What makes a great commit message?

What did we just do? (10 min / 0:50)

We've now created a new Git repository, done some work on a project and saved that work with Git! Let's recap:

Creating a New Repo:

The command for creating a new repo is git init (to initialize a new repo. This command creates a .git directory where Git will track and manages all the changes to the files in this directory.

You want to be careful where you run git init. You only want to run that command in a folder where you want to create a new repository. If you accidentally run it somewhere else, can you delete the repository by removing the .git directory (using rm -rf).

Saving Our Work:

Saving our work in Git requires two steps: Adding changes to the staging area and then committing those changes.

The staging area is one of Git's more unique features, and it can take some time to wrap your head around it. It helps to think of the staging area as a buffer between the working directory and the project history.

Why stage files?

Instead of automatically committing all of the changes you've made since the last commit, the staging area lets you group related changes into highly focused snapshots before actually committing to the project history. This means you can make all sorts of edits to unrelated files, then go back and split them up into logical commits by adding related changes to the stage and commit them piece-by-piece

Here's another way to think about it...

Git Local Diagram

Exercise 1.5: More Commits / History - You Do (5 min / 0:55)

  1. Modify index.html
  2. Add your changes to the staging area and create a new commit with an appropriate message.
  3. Create a new html file and stage and commit.
  4. View the commit history by running git log to see the log of commits, and what changed each commit changed.

TROUBLESHOOTING: If you've initialized the git repository in your sandbox directory instead of the resume folder, try running:

rm -rf .git


Break (10 min / 1:05)

Using Git to Work with Others (20 min / 1:25)

Git works really well as a version control tool but where it really shines is as a tool for collaboration (in combination with GitHub).

For the next couple of minutes, we're going to walk through a couple of scenarios and explain how Git and GitHub can help solve these scenarios.

Scenario 1

You have this awesome app idea, one that will definitely take off and become one of those "unicorn" apps worth billions and billions. You jump straight in to development and start working on the MVP on your laptop. You work through the night and get really far on your MVP, maybe 85% complete.

The next morning, you hop on your bike to come in to class so you can show your classmates and get their feedback. But on your bike ride in, you slip and fall! You are totally fine and uninjured. But you didn't realize your backpack was open and when you fell your laptop slide out, straight down a sewer drain! What can you do? You call 311 and the person on the phone tells you they don't respond to lost item calls.

How can Git and GitHub help?

GitHub complements Git by storing versions of a git repository on it servers, remotely. GitHub manages access to repositories and also provides many different services for interacting with repositories on GitHub. Repositories are associated with GitHub accounts, like yours. Unless .

You can create a remote repository in GitHub, link the remote with your local version using git remote commands like add, set-url, and remove. After that link is established, you are able to push changes from your local repository up to your remote repository on your GitHub account.

Scenario 2

Your friend lends you their laptop and you completely rebuild your MVP from scratch. This time however, you create a remote repository in GitHub to save your work there. You finish your MVP and go talk to a bunch of investors. One of them gives you a million dollars to finish building it out! 🤑 You decide hire all your WDI classmates to help you finish the app and take it to market.

After you figure out what features you want your classmates to build, one of them asks how they can start working on the codebase. You have the code on your laptop and on GitHub. How can your classmate (now coworker) get the code?

Since you're so flush with investor cash now, your first thought is to go and buy a bunch of fancy USB sticks with your company logo on them. Then, you can copy the codebase from your laptop on to each USB stick. It's a flawless idea!

How can Git and GitHub help?

USB sticks are a terrible idea.

GitHub is a tool for collaborating with other developers. Don't buy USB sticks, add your classmates as collaborators on the repository on GitHub. Then, they'll be able to clone the repository down to their laptops and push their changes back up. When you need work from one of your coworkers, you can easily pull it.

Scenario 3

The deadline you set with your investors is fast approaching and you still have a lot of work on your app that needs to be finished. It's time to hire some contractors to help push your app over the finish line!

You don't want to give the contractors privileged access to your app and you want some way to review their work before it gets merged into the final codebase. Maybe they should get the USB sticks?

How can Git and GitHub help?

USB sticks are still a terrible idea.

GitHub works well for all kinds of collaboration. Later in the course, we'll have an entire class dedicated to different collaboration workflows with GitHub.

What you want is for your contractors to fork your repository on GitHub: make a copy of the codebase that they own and control. They can make all the changes they need to, then ask for their work to be merged back into the original repository by making a pull request. You or one of your coworkers can review their pull request and merge it if everything looks good.

Scenario 4

You have finished building the feature you've set out to build. Now, your contractors have made their forks and are off finishing their own work.

You finish it up, push it to GitHub and then throw your hands up in the air. Eureka! You're finished. Time for a celebratory cup of coffee.

On your way to the gourmet coffee bar you bought with all that investor money, you get a call from one of the contractors. They need the work you just finished to make sure that their code works with yours.

They don't want it on a USB stick.

How can Git and GitHub help?

When your contractors fork the repository, they'll have a remote copy under their GitHub. They can clone that down and have a local and remote version of the repository of their own: their local is the copy on their laptop, their remote is the copy under their GitHub account (their fork).

Your recent work, however, is in the original repository. The original repository is the upstream repository for you contractors. You can set multiple remotes for a local repository, provided they are based off the same original repository. So your contractors just have to set the original repository as the upstream repository for their local repository and they'll be able to pull changes from it (but not push changes to it).


Your contractors finish up their work and you merge all their pull requests. You deploy the app and send the link to your investors.

Your investors are totally blown away by all the hard work you put in to building the app, congratulations!

We Do: Git and GitHub (5 min / 1:25)

We need a name for our startup (and repository). Head to Namium for some randomly generated startup names.

Creating your own remote repo (10 min / 1:35)

This relates to Scenario 1 from above

In this section, we'll learn to push changes made locally to our remote repo, hosted on our GitHub account.

How to Create a Remote Repository

  1. Go to GitHub
  2. In the top-right corner of the dashboard, you'll see a plus sign (+)
  3. Click on the plus sign and then on "New repository" from the dropdown menu
  4. Fill in the form for creating a new repo
  • You'll want to give it a name (something descriptive and memorable)
  • You'll generally want to keep the code public (especially for homework, labs and projects so your instructors can grade them)
  • You want to leave the checkbox that says "Initialize this repository with a README" unchecked
  1. Hit the "Create repository" button

Exercise 2: Publish to a remote repository on Github (15 min / 1:50)

This relates to Scenario 1 from above

The first step is to make sure you have SSH keys set up with GitHub so you don't have to type your password each time you want to push code. Generally speaking, SSH keys allows you to connect to a server without remembering a password.

To check whether you have SSH access set up with GitHub / GHE, run these two commands (don't include the $):

$ ssh -T
$ ssh -T

If you are already set up, you should see a response like:

Hi <username>! You've successfully authenticated, but GitHub does not provide shell access.

If you get Permission Denied, get help from the support instructor and reference this lesson.

How to publish to a remote repository on Github

  1. Make a new directory inside your sandbox/ directory with the same name as your remote repository from the previous step.
  2. Create an index.html file and "save" it (add and commit).
  3. Ensure you have at least one commit (git log to verify)
  4. Follow the steps provided to add repo as a remote and push your local commits to the remote repository
  • NOTE: there are 3 options for setting up your repo. take a second to think about which commands you need here
  • Hint: Does the repository on your LOCAL system already exist?
  1. Open the repo on GitHub and explore the code there
  2. Make a change locally, commit it, and push it
  3. Open the repo on Github, and note that the changes have synced (you may have to refresh)

Break (10 min / 2:00)

Forking (10 min / 2:10)

This relates to Scenario 3 from above and is generally how you will submit your homework

Pair up with your neighbor or the person behind you (Only pair up with 1 other person. If there is an odd number of students, someone can pair up with the instructor as a demo).

How to fork a repository

  1. Send your partner the link on GitHub to your repository (They should send you theirs)
  2. In the top right, below the plus-sign we used to create a new repository, there is a "Fork" button - click it.
  3. A modal may pop up with the title, "Where should we fork this repository?". If it does, click on your username.
  4. If everything works, you'll see a screen that has a book with a fork in it being scanned.
  5. You'll then be went to a page that looks like the one you were just on for your own repo. Take a close look at the heading in the top left: it should have your username and then the name of the repository and underneath that something like, "forked from <your_partners_uesername>/<the_name_of_the_repo>"

Cloning (10 min / 2:20)

This relates to Scenario 3 from above and is generally how you will submit your homework

Now that you've forked your partner's repository, you need some way to get it on to your computer (locally). This process is called cloning

How to clone a repository

  1. From the repo page for the fork of your partner's repository (where we left off in the previous step), find the green button that says "Clone or Download".
  2. Copy the link by highlighting it and hitting cmd + C or clicking on the clipboard button next to the link.
  3. Open up a new terminal window and navigate to your sandbox directory
  4. The command to clone a repository with git is git clone <url_for_the_repo_you_want_to_clone>. You can optionally pass in a name for the repository if you would like to name the working directory when you clone - don't worry about that right now though.
  5. Change in to your new directory and run git log to see the commit history.
  6. Run git remote -v. What do you get back? What is interesting about these links?

Pull Requests (10 min / 2:30)

This relates to Scenario 3 from above and is generally how you will submit your homework

Now that you've cloned your partner's repo, go a head and make a change to what ever file(s) they have. Stage and commit your work and then push it to the remote.

Where did we just push our changes to, our partner's repository on GitHub or our own?

If we want to contribute our work back to the original project, we need to do so with a pull request

How to make a pull request

  1. Push your work if you haven't already
  2. There are a couple of ways to make a new pull request:
  • From your fork, find and click the "New pull request" button (this is the fastest/easiest). This will take you to a new page with a "Create Pull Request" button.
  • From the original repository, click on the Pull requests tab and then click the New Pull Request button. Click on the "compare across forks" link, find your fork in the 3rd dropdown. Then click the "Create Pull Request" button.
  1. Give your pull request a title and a description. If this is a homework assignment, you should add your comfort level and completeness in the description and the title should include your full name.


  • Why is version control important for developers?
  • What problems do we anticipate using git / github?
  • Differentiate between git as a tool, and github as a service
  • Define and differentiate between forking and cloning

Quiz Questions

  1. What are the main components of a git repository and how do they relate?
  2. Describe the steps of the process for contributing to open source software on Github (the same as our homework submission process).


1. Visit the haiku repo and follow the instructions there.

In the comments of the Pull Request description, please include a block like so (numbers out of 5)...

comfort_level: 4
completeness: 5

2. Read Understanding git for real by exploring the .git directory

Optional but highly recommended!


Appendix - Git CLI Commands

Creating Repositories

  • git init - run this command in a folder to turn it into a git repository
    • note: don't init a repo inside an existing repo! (also don't init in your home folder) OR
  • git clone <URL> - download (clone) a repo from github (or other remote source)

Linking an existing repo to Github

  1. Create the repo on (make sure not to check the 'initialize with readme').
  2. Follow the instructions on the new repos webpage to add as a remote:
  3. Change directories to the local repo
  • cd ~/path/to/repo
  1. Add the github remote, and name it 'origin':
  • git remote add origin <URL>
  1. Push the existing commits up to the remote called 'origin' , and set it to track master branch:
  • git push -u origin master

Once linked, you can just run git push to push master branch to master branch


  1. Add the files you want to commit to the index (equivalent to checking which files you want to commit in the Github GUI app)
  • git add file1 file2 ..., or git add . will add all changes in the current folder
  1. Create the commit:
  • git commit -m "description message for commit"
  • if you omit the -m and message, then git will open an editor for you to write the message in

Syncing with a remote (push/pull)

  1. git pull [remote] [branch] - fetch and merge changes (from the origin and branch specified) and merge them into the current branch.
  • If origin and branch aren't specified, git will default to the tracking branch (usually origin and the remote branch with the same name as the current branch).
  • If no origin/branch are specified, and no tracking branch is set up, git may tell you to specify
  1. 'git push [remote] [branch]' - push and merge local changes from the current branch to the specified branch on the remote repo and branch specified.
  • Same rules apply as git pull above.