How to fetch a contribution branch to test it locally as an open-source maintainer

Hello Fellow CodeNewbies ,

In my last post, we were talking about how to fetch a branch from upstream repo as a contributor and test it locally.

And in this post, let's change the role.
If we were a maintainer of a repo, we would want to test the changes locally and see if things work as expected. Otherwise, we can encounter problems when we merge a contribution without testing it.
How can we do so?
I will walk you through the steps below.

Fetch a contribution branch

1. Add a remote repo for the forked repo

First of all, we need to add the contributor's forked repo as our remote repo.

  git remote add <remote-name> <fork-repo-url>

We can name the <remote-name> anything we want. I find it clearer for me to name this remote with the contributor's name or their GitHub username.
As an example:

  git remote add ayu <fork-repo-url>

Go to the contributor's fork repo on GitHub to copy their repo URL and paste it to replace the <fork-repo-url> part.

2. Check if the remote repo has been added.

Run this command to check our remote repos.

git remote -v

If the remote repo has been added, we should see:

origin <original-repo-url> (fetch)origin <original-repo-url> (push)ayu <fork-repo-url> (fetch)ayu <fork-repo-url> (push)

3. Fetch the forked repo to our local

Run this command to fetch the repo.

git fetch <remote-name>

So, in our case:

git fetch ayu

Now the contents of the repo, including the targeted branch, are fetched.
We will see something like this on our command line:

...* [new branch]      main           ->  ayu/main* [new branch]      some-branch    ->  ayu/some-branch* [new branch]      target-branch  ->  ayu/target-branch

But wait. There are two branches there.
How do we know which branch is pushed by the contributor to the repo and is asked for a merge?

How to find out the pushed branch

1. From the origin repo on GitHub, navigate to the Pull requests tab.
2. Click on the contributor's pull request.
3. Under the title of the pull request, next to the green "Open" button, we will see:

ayu wants to merge X commits into main from target-branch

From here we know that the branch that we want to navigate to is the target-branch.

4. Navigate to the branch

Run this command:

git checkout <branch-name>

In this example, it would be:

git checkout target-branch

We now can test out the changes from the contributor locally .

Thank you for reading!
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