Git: Complete Definition and Guide

What is Git?

Git is a distributed version control system created in 2005 by Linus Torvalds — the same creator as Linux — to manage the development of the Linux kernel. Facing limitations of existing tools, Torvalds designed Git with three goals: speed, data integrity, and support for distributed non-linear development. Twenty years later, Git has become the undisputed worldwide standard for code versioning.

Unlike centralised systems like SVN where a single server holds the complete history, Git is distributed: each developer holds a full copy of the repository, including the entire modification history. This architecture eliminates the single point of failure and enables offline work, local branching, and synchronisation only when appropriate.

Git works by taking "snapshots" of the complete project state at each commit, rather than storing differences between files. This model, combined with SHA-1 hashes to identify each commit, guarantees history integrity: any modification is detectable and traceable. It is this combination of performance, reliability, and flexibility that has made Git the universal versioning tool.

Why Git Matters

Git is much more than a simple code backup tool. It is the backbone of developer collaboration and the foundation of modern software development practices.

• Complete history and traceability: every change is recorded with its author, date, and explanatory message. You can return to any previous project state, compare versions, or identify the origin of a bug with commands like git bisect.
• Structured collaboration: the branching system allows multiple developers to work simultaneously on different features without interfering with each other. Merge requests (or pull requests) formalise the code review process before integration.
• Code security: with distributed copies of the repository, accidental code loss is virtually impossible. Even if the central server goes down, each developer holds a complete copy of the history.
• DevOps foundation: Git is the trigger for the entire modern CI/CD chain. A push to a branch can automatically launch tests, compilation, and production deployment.
• Living documentation: a well-maintained Git history with descriptive commit messages constitutes valuable documentation of the project's evolution and the technical decisions made.

How It Works

Git organises data into three main areas. The working directory contains files as you see and edit them. The staging area (index) is an intermediate zone where you select changes to include in the next commit. The local repository (.git) stores the entire history of commits, branches, and tags.

The typical Git workflow follows a simple cycle: you modify files in your working directory, add them to the staging area with git add, then create a commit with git commit. This commit is an immutable snapshot of the project state, identified by a unique SHA-1 hash. You then synchronise your work with the remote repository via git push.

Branching is Git's most powerful feature. Creating a branch is instant and costs almost nothing in terms of resources. This encourages using topic branches for each feature or bug fix. The main branch (main or master) stays stable, while development occurs on parallel branches that are merged after validation.

Concrete Example

At Kern-IT, Git is at the centre of our daily workflow. Each project has a Git repository hosted online, with a main branch that reflects the code in production. For each new feature or bug fix, a developer creates a dedicated branch, implements the changes, and submits a pull request for review by a colleague.

Our deployment process via Fabric relies directly on Git. The fab production deploy command connects to the server via SSH, executes a git pull to fetch the latest validated code from the main branch, installs new dependencies, runs database migrations, and restarts the application. This direct link between Git and deployment ensures that only validated and versioned code reaches production.

Implementation

1. Initialise the repository: start each project with git init or git clone. Configure the .gitignore file to exclude sensitive files (credentials, .env), compiled files, and dependency folders.
2. Adopt a branching strategy: use a model suited to team size. Git Flow for complex projects with planned releases, GitHub Flow (simpler) for continuous deployment.
3. Write descriptive commit messages: follow a clear convention (e.g., "Fix: correct VAT calculation on invoices") that explains the why of the change, not the what.
4. Practise pull requests: systematise code review before any merge to the main branch. This improves code quality and facilitates knowledge sharing.
5. Protect the main branch: configure protection rules requiring at least one pull request approval and passing automated tests before merging.
6. Automate with Git hooks: use pre-commit hooks to run linting and automatic formatting, and post-receive hooks to trigger deployments.

Associated Technologies and Tools

• GitHub / GitLab / Bitbucket: Git repository hosting platforms with collaboration features (pull requests, issues, CI/CD).
• CI/CD: continuous integration and deployment pipelines triggered by Git events.
• Fabric: SSH deployment tool that uses git pull to update code in production.
• Pre-commit: Git hooks framework for automating code quality checks.
• Git LFS: Git extension for managing large files (images, videos, datasets).

Conclusion

Git is the essential tool for every professional developer. Beyond simple versioning, it structures collaboration, secures code, and serves as the starting point for all modern DevOps practices. At Kern-IT, Git is deeply integrated into our value chain: from a developer's first commit to production deployment via Fabric, through code reviews in pull requests. Mastering Git means mastering the fundamentals of professional software development.