Part 3, Branches and Merging

Hands on Session - Part 3, Branches and Merging

• Branch Branching lets you have different versions of a repository at one time. By default, your repository has one branch named main (sometimes called master instead) that is considered to be the definitive/central branch. Typically a new branch is used to work on new features or bug fixes without affecting the main codebase until you are ready to merge the changes.

• Merge Merging combines changes from different branches into a single branch, typically changes are merged into the main branch.

_{^{Image taken from coderefinery: https://coderefinery.github.io/git-intro/branches/}}

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Part 3.1, Create a New Branch:

Now we'll create a new branch inside our repository.

git branch new-feature main

This means we'll create a new branch called new-feature using a copy of the current state of the main branch.

Now if we run:

git branch 

We'll see two branches, and the branch we are working on (main) indicated by an asterisk.

To swap to the other branch we can do:

git checkout new-feature

If you now run git branch again, you'll now see we're working in the new-feature branch.

Tip: you can combine the creation of a new branch and swapping to the branch is a single step:

git checkout -b new-feature main

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Part 3.2, Make a Commit in the New Branch and Merge them.

Add a new file and commit this file to the new branch.

Tip: Make sure you're working in the new-feature branch, you can check by typing: git branch.

Once you've made the commit, we first swap back to the main branch:

git checkout main

Then we merge the new-feature branch into the main branch:

git merge new-feature

At this point you should see the new file you created inside the main branch. You can also safely delete the new-feature branch (recommended, otherwise you'll end up with a large number of branches after a while which can be confusing).

git branch -d new-feature

If you run git branch now you should see the new-feature branch no longer exists.

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Part 3.3, Merge Two Branches Using a GitHub Pull Request

Now we'll repeat essentially the same process but this time instead of using the merge command in Git, we'll use GitHub's pull request feature instead.

1. Create the new branch and switch to it:

git checkout -b new-feature-pull main

1. Add a new file, commit the file, making sure you're in the new-feature-pull repository.

2. Push the new file to the remote repository.

Note that if we try to use just git push it wont work, instead we'll need to do:

git push -u origin new-feature-pull

It's not important right now to understand but the -u is short for --set-upstream option, which essentially sets up our git pull or git push commands for this new branch.

Now head over to GitHub and go to the main page of your repository, where you should see a message like this:

If we click to "compare and pull" we can start the pull request process.

This is best shown on the board, so I'll show this at the time and we can follow along. To revise the topic later on you can click here for a nice guide/tutorial

Once the pull request is successful we can go ahead and delete the old branch, you could do this on Git (as we saw in Part 3.2) or on GitHub.

This is typically how you merge branches when working with others. You can also use this method when working alone.

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End of Session

We've now gone through the basics of Git and GitHub. Several topics weren't covered in this session. Including dealing with merge conflicts and how to undo things. That said, you should have enough to get started. See the Intro and Appendix for some good sources to learn from.