GitHub is a web-based hosting service for version control using Git. At its core, Git is a free and open source distributed version control system. Distributed version control allows developers to work on local copies of repositories and synchronize their changes to remote repositories hosted on GitHub. This distributed workflow enables contributions from multiple developers without slowing down the development process.
When developers first obtain a copy of a Git repository, the full history of the project is downloaded to their local machine. This allows developers to work offline and commit changes locally. Local commits are stored in the project’s hidden .git directory with metadata about each commit. Commits contain a snapshot of the content of all files in the repository, but Git is smart enough to only store the differences from the previous version. This makes the history very small and efficient even for large projects.
Developers can make as many local commits as desired without affecting the remote repository. This empowering workflow is a core strength of Git and GitHub that enables flexible asynchronous collaboration. Local changes are kept completely isolated until developers choose to synchronize or “push” them to GitHub. To keep contributors from working simultaneously on the same lines of code, Git uses commits to record who made each change and when to avoid conflicts during synchronization.
To share changes with others and contribute to the project’s main codebase, developers need to interact with a remote repository. With GitHub, remote repositories are hosted on GitHub’s servers. Developers can create private repositories for their own work or open source repositories that anyone can access and contribute to. To synchronize local changes with a remote repository, Git uses lightweight synchronization called “pulling” and “pushing.”
Pulling fetches the latest changes from the remote repository and merges them into the local codebase. This allows developers to sync up and make sure their code is up to date before contributing changes of their own. Pushing uploads all local commits to the remote repository so others can access them. When synchronizing, Git intelligently determines what needs to be transferred between repositories and only sends the necessary commit metadata and file diffs.
If multiple contributors try to push changes simultaneously, Git avoids overwriting each other’s work through a process called “rebasing.” Rebasing works by taking all the commits from one branch and reapplying them on another in the proper order. For example, if one developer pushed to the main branch while another developer was working locally, Git would detect the conflict and force the local developer to pull and rebase to resolve the merge. This ensures everyone works off of the latest version of the code and merge conflicts are resolved locally before pushing.
Conflicts do occasionally occur if two developers modify the same line of the same file. Git cannot automatically determine which change should take precedence, so it flags a merge conflict that the developers need to resolve manually by choosing which changes to keep. After resolving conflicts locally, developers push the merged changes so the project continues to move forward together seamlessly.
Pull requests are a core part of collaboration on GitHub. When developers are ready for their changes to be reviewed and merged into the main codebase, they create a pull request. This invites other collaborators to review the proposed changes, discuss any issues, and vote to approve or reject the merge. Approved pull requests are automatically merged into the target branch once all reviews pass and any feedback is addressed to the satisfaction of all collaborators.
Pull requests allow open and transparent code reviews that improve quality while maintaining the flexibility of separate branches. Developers continue iterating independently on their own branches until the code is ready. GitHub syntax highlights diffs in pull requests so reviewers can easily see what code is changing line-by-line. If issues are found, conversations directly in the pull request provide a central place to discuss and resolve them before merging begins.
Once a pull request is approved and merged, the target branch like “main” or “master” is updated with all the commits from the pull request branch. Unlike many version control systems that delete source branches, branches on GitHub are preserved even after merging. This provides a permanent record of how the code evolved through the pull request process and enables convenient future work like hotfixes, translations and more without recreating branches from scratch. Preserved branches also allow reverting problematic merges using Git’s flexibility.
To summarize, GitHub combines the flexible decentralized workflow of Git with web-based tools that make collaboration seamless. Developers can work independently and commit changes locally without affecting others. Conflicts are resolved through rebasing and merging so the code continues evolving forward. Pull requests bring transparency to code reviews while branches provide reusable “paper trails” of evolution. These Version control superpowers enabled by GitHub have revolutionized how software is built by diverse distributed teams working together toward shared progress.