Common Git commands

Git Overview

Git is a version control system. Imagine working on a codebase with 3 engineers, (A,B,C)

3:00pm → A updates code with new feature

3:15pm → B updates code with new feature

3:16pm → A updates code with new feature

4:20pm → C updates code with new feature

5:00pm → You notice that your users are complaining about bugs in your app.

With git or other version control systems, upon noticing the bug you can revert the code to 4:20pm, 3:16pm, 3:15pm, or anytime in history to find a place where there is no bugs. Problem solved!

(This example is overly simplified)


Treat the curriculum like you have joined a new company and working on a new codebase. The first thing you should do is to download it onto your machine. To do this, you need to run git clone url-to-codebase. For C0D3 curriculum, the url is

After downloading the codebase, you should run git status to see which branch you are on, which will be master. Master branch will be where your most perfect code live (after getting reviewed), so you do not want to make any code changes on this branch. Instead, you should create a new branch.


Treat each problem like a new feature in the codebase. To start problem one, you want to create a new branch called p1 (which stands for problem 1). To do this, run git checkout -b p1 . After this, run git status to make sure you are indeed on p1 branch.


After solving problem 1 and passing all the tests, you should feel confident to save your code changes. To do this, there are 2 steps:

git add filename → Add all the files that you want to commit (aka save changes). If you are unsure of the files you have changed, run git status .

git commit -m 'your message here' → When you save your changes, it is necessary to describe what your changes are. This way, in the future you can read the history of commit messages to understand at a high level all the changes that happened.

git log → This commands display the history of commit messages. In this mode, use the arrow keys to scroll up and down and press q to return to the command prompt.

If a typo is discovered in your latest commit, use git commit --amend to correct the typo.

Starting a new feature / problem

After submitting a problem, you might be tempted to immediately start working on the next feature. This is not good. It is bad practice to submit 2 features together. Here is the correct way to start a new problem / feature:

  1. Go back to master branch (which does not have your solution to problem 1)
    1. git checkout master
  2. From master branch, create a new branch (ie: p2)
    1. git checkout -b p2


  • git clone url to download a codebase
  • git checkout -b branchname to create a new branch
  • git checkout branchname to switch to existing branch
  • git status to view your current branch and the files that are changed
  • git log to view commit message history
  • git commit --amend to edit the latest commit message
  • Commit!
    • git add filename to add the file you want to save
    • git commit -m 'message here' to save your changes and write a meaning message to describe your change

Common submission issues

Multiple solutions in a branch?

First, figure out which branch is the culprit. git checkout p1 to switch branches

Run git diff master to see what will be submitted. This compares the changes between the current branch and master. If everything looks good (only changes in one file), switch to a different branch and run the diff command again.

Once you have found the bad branch, the easiest solution is to delete the branch and submit again (if you've done it before, you can do it again!). To delete the branch, first go to master: git checkout master, then delete the offending branch: git branch -D your_offending_branch_name.

Now, from master, you can create a new branch git checkout -b whateverBranchItWas and then continue normally.

Check The Missing Semester if you want to learn more about git and other useful tools.

Edit this page on Github