Intro to PRs

You can use the following guide to learn how and why to create a pull request.

What is a pull request?

A pull request is a way to suggest changes to a repository. When you create a pull request, you propose your changes and request that someone review and pull in your contribution and merge them into their branch. Pull requests show differences between the content from both branches and the changes are visible in the repository.

Set up your environment

Create a local copy of the repository

Copy the following file to a new Git repo.

cd ~/source/repos
git init my-first-pr
cd my-first-pr
cp ~/Downloads/README.md .

Important Note: If you get an error because the file is missing, then do the following:

ls -l ~/Downloads/README*.md 

This will show if you have more than one ReadMe file. For example:

-rw-r--r-- 1 AD+5001775 536871425 5679 Aug 19 > 12:55 '/c/Users/5001775/Downloads/README(1)(1).md'

In this situation we need to copy the file an > rename it in one go using:

cp ~/Downloads/README(1)(1).md ReadMe.md

IMPORTANT: Please ensure you continue working on the file copy and not the original.

To do this, close this file and then at the command line type the following:

code .

or use the file explorer to locate and open the repository's copy of the ReadMe.md file.

Create an empty repository on GitHub

1. Go to GitHub and sign in.
2. In the upper-right corner of any page, select ➕, and then select New repository.
3. Name your repository my-first-pr. IMPORTANT: Do not initialize the repository with a README, .gitignore, or license.
4. Note the name of your repository URL here: You'll need this information later.

Add the remote repository

1. In the terminal, add the URL of the repository you created on GitHub as the remote repository.

git remote add origin <URL>

2. Check that the remote repository was added.

git remote -v

3. Consider why it does not provide a URL for pull, only push and fetch?

---

4. Push the local repository to the remote repository.

   git push -u origin main

Important

You will get an error if you have not added the updated ReadMe.md file and then committed it... So if that is the case make sure you do a git add ReadMe.md and then commit it using git commit -m "init: start of exercise".

Once you have done this, use the git push -u origin main again.

5. Refresh the GitHub page for your repository. You should see this README.md file.

Why are pull requests called "Pull Requests"? (wrong answer)

Pull requests are so named basically because you are asking to pull changes from a remote to your local repository. And that's because you have to ask permission to copy changes out of the repository, even if you have read access to that repository.

Create a local branch

You read the definition above, and you can't believe they got it this wrong. The name Pull Request can be misleading, but come on!

You decide to fix the definition above, but BEFORE you do that, you need to create a new branch to work on.

1. Create a new branch and switch to it.

# Older style:
git checkout -b fix/pr-definition
# Or, newer style:
git switch -c fix/pr-definition

2. Edit this file and address the two TODO items in two separate commits.

git commit -am "Add forks to the PR definition"
git commit -am "Give correct reason to why PRs are named that"

3. Check on GitHub whether the branch exists there or not. Does it? Why or why not?
4. You may think it is because you haven't pushed to the branch yet, so go ahead and try to push the branch to the remote repository.

git push

You probably got a similar error to this:

fatal: The current branch fix/pr-definition has no upstream branch

5. What does this error mean? Why did it happen? Git explains how to fix it by running a command that will:

   1. Create a new branch on the remote repository with the same name as the local branch (if the remote branch doesn't already exist).
   2. Set the local branch to track the remote branch.
   3. Push the local branch to the remote repository.

6. Run the command that Git suggests to fix the error. There is also a shorthand for this command:

git push -u origin fix/pr-definition

7. Refresh the GitHub page for your repository. You should see the new branch there. GitHub will also suggest that you create a pull request. Do you see that?

Create a pull request

1. Select Compare & pull request.

2. Note that the base repository and compare branch are correct.

3. Add a title and description for your pull request. Here is an example of a high-quality pull request description:

   Title: Fix PR definition
   Description: This pull request fixes the definition of a pull request. It adds information about forks and corrects why pull requests are called "pull requests".

4. Select Create pull request.

Review and merge a pull request

1. Go to the Pull requests tab on the repository page.
2. Select the pull request you created.
3. Review the changes in the pull request. You can see the commits that were added to the branch. You can also view the changes in the Files changed tab.
4. Add a comment to the pull request. Please feel free to ask for more information, suggest changes, or approve the pull request.
5. Select Merge pull request to merge the changes into the main branch.

Notice that GitHub suggests that you delete the branch after merging. This is a good practice because it keeps your repository clean and easy to navigate. It is part of a Git workflow called GitHub flow.

Add the Picture

Follow the concepts you pacticed above, using the steps below with a new branch fix/add-image.

In this exercise you will:

• create a new branch fix/add-image and switch to the new branch
• copy the colag.png file to the repository folder using cp colab.png ./
• add the image to version control using git add
• commit the change to the repository using git commit -m "fix: Add image for ReadMe.md banner"
• push the changes the remote fix/add-image branch
• create a pull request to merge the fix into the main branch
• merge the pull request with a comment of image accepted for ReadMe
• check the ReadMe now has the iamge visible
• Once all done, delete the fix/add-image branch as it is no longer needed.

Optional: Fork someone else's repository and create a pull request

If you are doing this in class, you can fork the repository of the person sitting next to you. If you are doing this on your own, you can fork a friend's or colleague's repository.

When you fork their repo, examine their definition and try to improve on it, then create a pull request to suggest your changes on their repository.