Git is a distributed version control system that allows multiple people to work on a project at the same time without overwriting each other's changes. It was created by Linus Torvalds in 2005 to manage the development of the Linux kernel. GitHub, on the other hand, is a web-based hosting service for Git repositories. It provides a graphical interface for managing repositories and includes features like issue tracking, pull requests, and code review.
The GitHub flow is a lightweight, branch-based workflow that supports teams and projects where deployments are made regularly. This guide explains how the GitHub flow works, and how it can be used in various software development scenarios.
Understanding Git
Before we delve into the GitHub flow, it's important to understand the basics of Git. Git is a distributed version control system, which means that every developer's working copy of the code is also a repository that can contain the full history of all changes. This is in contrast to centralized version control systems, where there is a single, central repository.
Git's distributed nature allows for several benefits. For one, it allows developers to work offline, since they have a full copy of the repository. It also allows for multiple workflows, like the GitHub flow, which we'll discuss later.
Git's History
Git was created by Linus Torvalds in 2005. Torvalds, the creator of the Linux kernel, developed Git to manage the kernel's development. Before Git, the Linux kernel was managed using a proprietary distributed version control system called BitKeeper. However, due to a dispute with the company that developed BitKeeper, Torvalds decided to create his own system.
Since its creation, Git has become one of the most popular version control systems. It's used by millions of developers around the world, and it's the system behind GitHub, one of the most popular code hosting platforms.
Git's Key Features
Git has several key features that make it a powerful tool for software development. One of these is its branching model. Git allows for easy branching and merging, which makes it ideal for workflows like the GitHub flow. Branches are used to develop features isolated from each other. The master branch is the "default" branch when you create a repository. Use other branches for development and merge them back to the master upon completion.
Another key feature of Git is its distributed nature. As mentioned earlier, every developer's working copy of the code is a full-fledged repository with complete history and full version tracking capabilities, independent of network access or a central server. This allows for a decentralized workflow, where developers can work independently and have their changes merged later.
Understanding GitHub
GitHub is a web-based hosting service for Git repositories. It provides a graphical interface for managing repositories, making it easier for developers to use Git. GitHub also includes features like issue tracking, pull requests, and code review, which can help teams collaborate more effectively.
GitHub was founded in 2008 by Tom Preston-Werner, Chris Wanstrath, and PJ Hyett. Since then, it has grown to become one of the largest code hosting platforms in the world. In 2018, GitHub was acquired by Microsoft.
GitHub's Key Features
GitHub has several key features that make it a powerful tool for software development. One of these is its support for the Git version control system. GitHub provides a graphical interface for managing Git repositories, making it easier for developers to use Git. It also provides access control and several collaboration features, such as wikis and basic task management tools for every project.
Another key feature of GitHub is its support for pull requests. Pull requests let you tell others about changes you've pushed to a branch in a repository on GitHub. Once a pull request is opened, you can discuss and review the potential changes with collaborators and add follow-up commits before your changes are merged into the base branch.
The GitHub Flow
The GitHub flow is a lightweight, branch-based workflow that supports teams and projects where deployments are made regularly. It's centered around the idea of using branches for feature development and then using pull requests to initiate code review and discussion about the changes before they're merged into the master branch.
The GitHub flow has six steps: create a branch, add commits, open a pull request, discuss and review your code, deploy, and merge. Each of these steps is designed to support a collaborative, iterative development process.
Creating a Branch
The first step in the GitHub flow is to create a branch. When you create a branch in your project, you're creating an environment where you can try out new ideas. Changes you make on a branch don't affect the master branch, so you're free to experiment and commit changes, safe in the knowledge that your branch won't be merged until it's ready to be reviewed.
Branches are also useful for developing features in isolation. By creating a new branch for each feature, you can ensure that the master branch always contains production-ready code.
Adding Commits
Once you've created a branch, you can start making changes to your project. Whenever you add, edit, or delete a file, you're making a commit, and adding them to your branch. This process of adding commits keeps track of your progress as you work on a feature branch.
Commits also create a transparent history of your work that others can follow to understand what you've done and why. Each commit has an associated commit message, which is a description explaining why a particular change was made. Furthermore, each commit is considered a separate unit of change. This makes it easy to roll back changes if a bug is discovered, or if you decide to head in a different direction.
Opening a Pull Request
Pull Requests initiate discussion about your commits. Because they're tightly integrated with the underlying Git repository, anyone can see exactly what changes would be merged if they accept your request.
You can open a Pull Request at any point during the development process: when you have little or no code but want to share some screenshots or general ideas, when you're stuck and need help or advice, or when you're ready for someone to review your work. By using GitHub's @mention system in your Pull Request message, you can ask for feedback from specific people or teams, whether they're down the hall or 10 time zones away.
Discussing and Reviewing Code
Once a Pull Request has been opened, the person or team reviewing your changes may have questions or comments. Perhaps the coding style doesn't match project guidelines, the change is missing unit tests, or maybe everything looks great and props are in order. Pull Requests are designed to encourage and capture this type of conversation.
You can also continue to push to your branch in light of discussion and feedback about your commits. If someone comments that you forgot to do something or if there is a bug in the code, you can fix it in your branch and push up the change. GitHub will show your new commits and any additional feedback you may receive in the unified Pull Request view.
Deployment
With GitHub, you can deploy from a branch for final testing in production before merging to master. Once your pull request has been reviewed and the branch passes your tests, you can deploy your changes to verify them in production. If your branch causes issues, you can roll it back by deploying the existing master into production.
Deploying from a branch enables you to solve problems quickly before your changes are merged into master. This step is optional and may not suit all projects; it depends on how you manage deployments and what tools you use.
Merging
Now that your changes have been verified in production, it is time to merge your code into the master branch. If it was a particularly large or important change, you might want to rebase and squash your commits to keep the history clean.
Once merged, Pull Requests preserve a record of the historical changes to your code. Because they're searchable, they let anyone go back in time to understand why and how a decision was made.
Use Cases of GitHub Flow
The GitHub flow can be used in various software development scenarios. It's particularly useful for projects where deployments are made regularly, as it allows for continuous integration and continuous deployment (CI/CD). The GitHub flow can also be used in open source projects, where it allows for easy collaboration between contributors.
For example, a team working on a web application could use the GitHub flow to manage the development of new features. Each feature would be developed on a separate branch, and once the feature is complete, a pull request would be opened for code review. Once the code has been reviewed and tested, it can be merged into the master branch and deployed.
Specific Examples
Let's consider a specific example. Suppose you're working on a web application, and you're tasked with adding a new feature. You would start by creating a new branch for the feature. Then, you would make changes to the code and commit them to the branch. Once the feature is complete, you would open a pull request and ask your teammates to review your code.
After your teammates have reviewed your code and given their approval, you would merge your branch into the master branch. Then, you would deploy the application with the new feature. If any issues arise, you can quickly fix them by making additional commits to the master branch.
Another example could be an open source project. Suppose you're a contributor to an open source project, and you want to fix a bug or add a new feature. You would start by forking the repository and creating a new branch. Then, you would make changes to the code and commit them to your branch. Once you're done, you would open a pull request and ask the project maintainers to review your changes. If they approve your changes, they would merge your pull request, and your changes would be included in the project.
Conclusion
The GitHub flow is a powerful tool for managing software development projects. It's a lightweight, branch-based workflow that supports teams and projects where deployments are made regularly. By using the GitHub flow, teams can work collaboratively, review each other's code, and deploy regularly.
Whether you're working on a small team, contributing to an open source project, or working on a large enterprise project, the GitHub flow can help you manage your work effectively. By understanding how it works and how to use it, you can improve your software development process and produce better code.