Pushing changes to GitHub

Overview

Questions

• How do I share my changes with others on the web?

Objectives

• Push to or pull from a remote repository.

Local vs Remote Repositories

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Version control really comes into its own when we begin to collaborate with other people. We already have most of the machinery we need to do this; the only thing missing is to copy changes from one repository to another.

Systems like Git allow us to move work between any two repositories. In practice, though, it’s easiest to use one copy as a central hub, and to keep it on the web rather than on someone’s laptop. Most programmers use hosting services like GitHub, Bitbucket or GitLab to hold those main copies; we’re using GitHub.

Before we share our changes, let’s first look at our planets repo on GitHub.

Even though we have made changes to our local copy of planets, the remote copy on GitHub still looks empty. This is because we have not yet “pushed” our changes (or commits) to the remote repository.

If you remember back to the previous episode where we added and committed our earlier work on mars.txt, we had a diagram of the local repository which looked like this:

The Local Repository with Git Staging Area

Taking into account the two repositories, we need a diagram like this:

Freshly-Made GitHub Repository

Callout

Note that our local repository still contains our earlier work on mars.txt, but the remote repository on GitHub appears empty as it doesn’t contain any files yet.

Because we created our repo on GitHub first and then cloned it to our local computer, the two repositories are already connected. If we had instead created the local repo first, then the remote repo on GitHub, we would need to manually connect the two repos, with a commmand like:

BASH

$ git remote add origin git@github.com:vlad/planets.git

origin is a local name used to refer to the remote repository. It could be called anything, but origin is a convention that is often used by default in git and GitHub, so it’s helpful to stick with this unless there’s a reason not to.

Instead, we can simply verify that the two repositories are connected with the command:

BASH

$ git remote -v

OUTPUT

origin   git@github.com:vlad/planets.git (fetch)
origin   git@github.com:vlad/planets.git (push)

Pushing local changes to GitHub

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This command will push the changes from our local repository to the repository on GitHub:

BASH

$ git push origin main

OUTPUT

Enumerating objects: 16, done.
Counting objects: 100% (16/16), done.
Delta compression using up to 8 threads.
Compressing objects: 100% (11/11), done.
Writing objects: 100% (16/16), 1.45 KiB | 372.00 KiB/s, done.
Total 16 (delta 2), reused 0 (delta 0)
remote: Resolving deltas: 100% (2/2), done.
To https://github.com/vlad/planets.git
 * [new branch]      main -> main

Our local and remote repositories are now in this state:

GitHub Repository After First Push

We can pull changes from the remote repository to the local one as well:

BASH

$ git pull origin main

OUTPUT

From https://github.com/vlad/planets
 * branch            main     -> FETCH_HEAD
Already up-to-date.

Pulling has no effect in this case because the two repositories are already synchronized. If someone else had pushed some changes to the repository on GitHub, though, this command would download them to our local repository.

Let’s verify that our changes made it to GitHub: go to your browser window with the GitHub repo and refresh the page. You should now see the mars.txt file. Click on the file, and you can see the contents of the file are the same as in VS Code.

Now click on the “History” link. You should see each commit made to the file, even though we only pushed once.

Key Points

• “A local Git repository can be connected to one or more remote repositories.”
• “git push copies changes from a local repository to a remote repository.”
• “git pull copies changes from a remote repository to a local repository.”