Version Control with Git



Teaching: 25 min
Exercises: 30 min
  • How can I use version control to collaborate with other people?

  • Clone a remote repository.

  • Collaborate pushing to a common repository.

For the next step, get into pairs. One person will be the “Owner” and the other will be the “Collaborator”. The goal is that the Collaborator add changes into the Owner’s repository. We will switch roles at the end, so both persons will play Owner and Collaborator.

Practicing By Yourself

If you’re working through this lesson on your own, you can carry on by opening a second terminal window. This window will represent your partner, working on another computer. You won’t need to give anyone access on GitHub, because both ‘partners’ are you.

The Owner needs to give the Collaborator access. On GitHub, click the settings button on the right, then select Collaborators, and enter your partner’s username.

Adding Collaborators on GitHub

To accept access to the Owner’s repo, the Collaborator needs to go to Once there she can accept access to the Owner’s repo.

Next, the Collaborator needs to download a copy of the Owner’s repository to her machine. This is called “cloning a repo”. To clone the Owner’s repo into her Desktop folder, the Collaborator enters:

$ git clone

Replace the URL with the correct URL from the owner.

After Creating Clone of Repository

The Collaborator can now make a change in her clone of the Owner’s repository, exactly the same way as we’ve been doing before:

$ cd ~/Desktop/vlad-conversion
$ nano
$ cat
> > # My Conversion Tools
> >
> > def dollars2cents(dollars):
> >     cents = dollars * 100
> >     return cents
$ git add
$ git commit -m "Implement dollars2cents function"
 [master fc7397d] Implement dollars2cents function
 1 file changed, 2 insertions(+), 1 deletion(-)

Then push the change to the Owner’s repository on GitHub:

$ git push
Counting objects: 3, done.
Delta compression using up to 24 threads.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 335 bytes | 0 bytes/s, done.
Total 3 (delta 1), reused 0 (delta 0)
remote: Resolving deltas: 100% (1/1), completed with 1 local objects.
   2e763f1..fc7397d  master -> master

Take a look to the Owner’s repository on its GitHub website now (maybe you need to refresh your browser.) You should be able to see the new commit made by the Collaborator.

To download the Collaborator’s changes from GitHub, the Owner now enters:

$ git pull
remote: Counting objects: 4, done.
remote: Compressing objects: 100% (2/2), done.
remote: Total 3 (delta 0), reused 3 (delta 0)
Unpacking objects: 100% (3/3), done.
 * branch            master     -> FETCH_HEAD
Updating 9272da5..29aba7c
Fast-forward | 3 ++-
 1 file changed, 2 insertion(+), 1 deletion(-)
 create mode 100644 pluto.txt

Now the three repositories (Owner’s local, Collaborator’s local, and Owner’s on GitHub) are back in sync.

A Basic Collaborative Workflow

In practice, it is good to be sure that you have an updated version of the repository you are collaborating on, so you should git pull before making our changes. The basic collaborative workflow would be:

It is better to make many commits with smaller changes rather than of one commit with massive changes: small commits are easier to read and review.

Switch Roles and Repeat

Switch roles and repeat the whole process.

Review Changes

The Owner push commits to the repository without giving any information to the Collaborator. How can the Collaborator find out what has changed with command line? And on GitHub?

Comment Changes in GitHub

The Collaborator has some questions about one line change made by the Owner and has some suggestions to propose.

With GitHub, it is possible to comment the diff of a commit. Over the line of code to comment, a blue comment icon appears to open a comment window.

The Collaborator posts its comments and suggestions using GitHub interface.

Version History, Backup, and Version Control

Some backup software can keep a history of the versions of your files. They also allows you to recover specific versions. How is this functionality different from version control? What are some of the benefits of using version control, Git and GitHub?

Key Points