jarednielsen.com

Learn Git Branch Workflow

February 11, 2019

Learn Git Branch Workflow

One of the most useful aspects of Git is the ability for developers to create branches of a project to test new features and fix bugs without modifying the code in production. Each repository has at least one if not more branches. When you initialize a new repository, a master branch is created by default. Git allows you to create branches that stem from the trunk of your project. A branch, at its core (no pun intended), is a unique series of code changes with a unique name. Your branch name should be descriptive, so that you and your collaborators can easily infer the work being done. If you’re just joining us, you may want to Learn Git Workflow Basics or Learn Git Workflow Centralized Collaboration

In this tutorial, you will learn:

  • How to create and checkout a branch
  • How to merge branches
  • How to delete branches
  • How to push a branch to a remote origin
  • How to open a pull request
  • How to resolve conflicts using the Git branch workflow

This tutorial is divided into two parts. The first part walks you through the basics of a Git branch workflow. The second part is designed for collaborating with a partner using the Git branch workflow. You don’t need a partner to follow along, but you won’t be able to complete all of the operations unless you configure two separate Github accounts.

Can’t find a partner? Hit me up @jarednielsen

Initializing a Repository

On GitHub.com, create a new repository git-workflow-branching

Initialize with a README

On the landing page of your repository, note that you have 1 branch named master.

From the command line,

git clone <URL to git-workflow-branching>
cd git-workflow-branching

Git Branch Workflow

Run the following command to see all your branches:

git branch

The output will be:

* master

By default, the first branch is called master. The asterisk alerts us to which branch we are currently in. There’s one very important rule in the Git branch workflow: anything in the master branch is always deployable. Because of this, it’s extremely important that your new branch is created off of master when working on a feature or a fix.

To create a new branch, named dev, type the following:

git checkout -b dev

You’ll receive this message:

Switched to a new branch 'dev'

And if you run git branch again the output will be:

* dev
  master

The git checkout command lets you navigate between the branches created by git branch. Checking out a branch updates the files in the working directory to match the version stored in that branch, and it tells Git to record all new commits on that branch. Think of it as a way to select which line of development you’re working on. The -b flag allows you to simultaneously checkout and create a branch. You can also create a branch using

git branch <name-of-branch>

This does not ‘checkout’ the branch, though. Try it.

git branch test
git branch

Your output should be:

* dev
  master
  test

You are still working in the dev branch, even though you created a new branch test.

To delete a branch:

git branch -d test

Verify that test is gone

git branch

You can switch back and forth between your two branches, by using the git checkout command:

git checkout master
git checkout dev

Every time you begin working on your project, run

git checkout master
git pull

Every time!

Why?

  1. So you know where you are and you don’t start working in the wrong branch.
  2. So your local repo is up to date with the remote.

So what’s the habit you’re going to make?

git checkout master
git pull

Merging Branches

Now, switch to your dev branch if you’re not already there.

git checkout dev

Create a new file

touch index.html

Add and commit the file

git add index.html
git commit -m “Add index”

The new file is now committed to our dev branch.

Run ls to view all files in the dev branch.

Switch to your master branch

git checkout master

And list (ls) all files.

What’s missing?

index.html.

Let’s merge the file from dev into our master branch.

git merge dev

The merge command does what? You guessed it. For educational purposes, let’s verify that index.html was in fact merged from dev to master.

ls

Yo la tengo!

What does Fast-forward mean? When we merged our dev branch it was ahead of our master branch, so Git fast-forwarded our master branch to catch up to the changes we merged from dev.

Now push to the remote:

git push

Pull Requests

Back at GitHub.com, you will see that index.html is now in our remote repository. But we still only have one branch. Our dev branch didn’t push.

Back at the Terminal, switch to your dev branch.

git checkout dev

Add a new file

touch server.js
git add server.js
git commit -m “server.js”

If you run git push, you will receive this error:

fatal: The current branch dev has no upstream branch.

To push the current branch and set the remote as upstream, use

git push --set-upstream origin dev

While the solution this prompt offers works, it isn’t best practice for our workflow model. Instead, we only need to push our new branch to our origin:

git push origin dev

Go back to your repo on GitHub.com. You will see that you now have two branches, Using the Branch toggle, you can switch back and forth between your branches and see the changes that exist between them.

Either click the green Compare & pull request button or select the branches tab and under your dev branch click New pull request. This will route you to a page where you can compare the changes between branches and merge the two. Add a useful comment and click Create Pull Request. You will be routed to another page where you can confirm the merge.

Return to the landing page for your repo and you will see that server.js is now in your master branch.

Back at your Terminal, switch to your master branch.

git checkout master

And update your repo locally.

git pull

Best practice with branches is to delete them once the work has been merged. First delete it remotely:

git push --delete origin dev

Then delete it locally. (Note: you can’t be in the branch you want to delete and if the branch is not empty, you need to use the -D switch.)

git branch -D dev

Now

git branch

You should only have master. Verify that it is in fact removed from your remote repo.

Cool beans? Now find a friend.

Collaborative Git Workflow with Branches

Partner 1

In your master branch, create a .gitignore for your project.

touch .gitignore

Don’t forget the . at the beginning of the file name.

Open this in your IDE and add the following:

node_modules

Save, add, commit and push.

What is .gitignore doing?

Now that we are working with packages, your applications will always need a .gitignore.

On GitHub.com, under Settings, select the Collaborators menu option in the left sidebar.

In the field in the Collaborators panel, search for your partners GitHub account and click Add collaborators.

This will send an email to your partner. Alternatively, you can select the Copy invite link option and send it by other means.

Partner 2

Accept the invitation and clone your partner’s repo:

rm -rf git-workflow-branching
git clone <URL-to-partners-git-workflow-branching>
cd git-workflow-branching

Now create a branch called “new-feature”

git checkout -b new-feature

Open server.js in your IDE and add boilerplate Express app code:

var express = require("express");

var app = express();
var PORT = 3000;

app.get("/", function(req, res) {
  res.send("I love Git!");
});

app.listen(PORT, function() {
  console.log("App listening on PORT " + PORT);
});

Save, add, and commit. When you run git push, you’re going to get this error:

fatal: The current branch new-feature has no upstream branch.

To push the current branch and set the remote as upstream, use

git push --set-upstream origin new-feature

What do you need to do?

git push origin new-feature

Now go to GitHub.com. You will see that your branch, new-feature, is now added to the remote repo. Make a pull request with a useful comment. Let your partner know you’ve made the pull request, but don’t merge it.

Partner 1

You should receive an email informing you that your partner made a pull request. Click the link in the email to review it on GitHub. Alternatively, navigate to the Pull requests tab via the landing page of your repo. You will see this message: This branch has no conflicts with the base branch

So go ahead and merge the pull request.

Partner 2

Check your email. You should receive a notification that your pull request was merged. You can follow the link to see the details.

Resolving Conflict in the Git Branch Workflow

Both Partners

If only it was always this easy. Let’s make some conflict!

What are the first two things you need to do before working on a project?

git checkout master
git pull

Partner 1

Create a branch to work on:

git checkout -b another-feature

Open server.js in your IDE and replace res.send() in the GET method to res.sendFile()

app.get("/", function(req, res) {
  res.sendFile(path.join(__dirname, "index.html"));
});

Don’t forget to add the path package to your app:

var path = require("path");

Save, add, commit, push.

Yup.

You need to add the upstream to remote.

Partner 2

Navigate to the repo on GitHub.com. In the Branches tab, under Active, you will see the new branch another-feature. Click the New pull request button. Towards the bottom of this page, you should see something like this:

@@ -1,10 +1,11 @@

var express = require("express");
+  var path = require("path");

var app = express();
var PORT = 3000;

app.get("/", function(req, res) {
-  res.send("I love Git!");
+  res.sendFile(path.join(__dirname, "index.html"));
});

app.listen(PORT, function() {

Your partner’s changes and additions are highlighted in green and deleted code is highlighted in red. If you agree with what your partner did, leave a useful comment such as, “Nice! Now we need some HTML to serve!’, and create the pull request. On the next page, Merge and Confirm.

Nice! Now we need some HTML to serve!

On GitHub.com, navigate to your index.html file.

Click the pencil icon to edit the blank file and copy/paste the following code into the editor:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title></title>
  </head>
  <body>
    <h1>I love Git!</h1>
  </body>
</html>

Commit the changes by clicking the big green button at the bottom of the screen.

Both Partners

What’s the first thing you do when sitting down to work on your application?

git checkout master
git pull

Learn Git Fork & Pull Request Workflow

In the next tutorial you will Learn Git Fork & Pull Request Workflow.


Jared Nielsen

When we force code to act out of the ordinary… that’s where the magic happens. That’s when we make art. @jarednielsen