Git is a distributed version control system (DVCS) that allows software engineers to track changes in source code during software development. It is designed to handle everything from small to very large projects with speed and efficiency. Git is easy to learn and has a tiny footprint with lightning fast performance. It outclasses SCM tools like Subversion, CVS, Perforce, and ClearCase with features like cheap local branching, convenient staging areas, and multiple workflows.
Created by Linus Torvalds in 2005 for development of the Linux kernel, Git is the most widely adopted version control system for software development. With a distributed approach, it allows every developer to have a full copy of the project history on their local machine, enabling easy branching and merging, and promoting workflows that improve project velocity and code quality.
Git Architecture
Git's architecture is a key part of its design philosophy. It is built to support a distributed workflow, where developers can work independently on their own local repositories, then share or synchronize their changes with others. This is different from centralized version control systems, where there is a single, central repository that everyone works off of.
Git's architecture is built around a simple key-value data store. Every piece of content is identified by a unique key, which is a SHA-1 hash of the content. This means that the content is intrinsically tied to its identifier, making it virtually impossible to change the content without changing the identifier. This is a fundamental part of how Git ensures data integrity and supports distributed workflows.
Repository
A Git repository is a .git/ folder inside a project. This repository tracks all changes made to files in your project, building a history over time. This means that you can revert to older versions of your project, compare earlier versions, and see who modified something and when.
Each Git repository is self-contained, and it has complete history and full version tracking capabilities, independent of network access or a central server. The repository holds all the data for the full history of the project and all the necessary information about the project's progress.
Commits
Commits are the heart of Git's version control mechanism. A commit, or "revision", is an individual change to a file (or set of files). It's like when you save a file, except with Git, every time you save it creates a unique ID (a.k.a. the "SHA" or "hash") that allows you to keep record of what changes were made when and by who. Commits usually contain a commit message which is a brief description of what changes were made.
When you make a commit, Git stores a commit object that contains a pointer to the snapshot of the content you staged, the author and message metadata. This object also contains zero or more pointers to the commit or commits that were the direct parents of this commit: zero parents for the initial commit, one parent for a normal commit, and multiple parents for a commit that results from a merge of two or more branches.
Git Workflow
Git's workflow revolves around the concept of branches. Branching is a feature available in most modern version control systems. Git branches are effectively a pointer to a snapshot of your changes. When you want to add a new feature or fix a bug—no matter how big or small—you spawn a new branch to encapsulate your changes.
This makes it harder for unstable code to get merged into the main code base, and it gives you the chance to clean up your future's history before merging it into the main branch.
Branching
Branching in Git is a lightweight, fast process. It's essentially a pointer to a specific commit, along with an automatic update to the pointer as new commits are made. 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 branch upon completion.
Branches are a core concept in Git, and it's the way to concurrently work on different features or parts of a project. They also help in managing the process of merging code back into the master branch, and can be used to test out experiments without the fear of ruining your main project.
Merging
Merging is the way to get the divergent lines of development back together. The git merge command lets you take the contents of another branch (or any commit, for that matter) and integrate it with your current branch. A conflict arises when the commit that has to be merged has some change in one place, and the current commit also has a change at the same place. Git cannot automatically decide which version to take. Therefore, conflict resolution is a user responsibility.
Git offers tools to help navigate this process, and when conflicts are resolved, the result is a new commit on the current branch that includes the changes from the merged branch.
Git Commands
Git commands are used to perform operations on the Git repositories. These operations include creating a repository, making changes to the repository, viewing the history of the repository, and synchronizing the repository with remote repositories. Git commands are executed from the command line interface (CLI).
Some of the most common Git commands include git init, git clone, git add, git commit, git push, git pull, and git branch. Each of these commands performs a specific operation and has a set of options that modify their behavior.
git init
The git init command is used to create a new, empty repository. It's the first command you'll use when starting a new project. You can run it in an existing project directory to turn it into a Git repository, or in a new directory to create a new repository.
The command creates a .git directory in the current directory, which contains all the necessary metadata for the new repository. This metadata includes subdirectories for objects, refs, and template files. A HEAD file is also created which points to the currently checked out commit.
git clone
The git clone command is used to create a copy of a remote repository. This is typically used to get a local copy of a project that you're going to work on. The clone includes all the project's files, history, and branches.
Git clone is also used to create a backup of a repository. The clone command downloads an existing Git repository to your local computer. You will then have a full-blown, local version of that Git repo and can start working on the project.
Git's Importance in Software Development
Git is a critical tool in modern software development for a few reasons. First, it allows a large number of developers to work simultaneously on a project without stepping on each other's toes. Second, it makes it easy to roll back to previous versions of a project, which is crucial for bug tracking and fixing.
Furthermore, Git's distributed nature allows developers to work offline and not rely on a central server to store all versions of a project’s files. This means that even if you're working on a small piece of a project, you have a full copy of the project at your fingertips if you need it.
Collaboration
Git's distributed nature makes it an excellent tool for collaboration. Every developer has their own local repository, complete with a full history of commits. This means that if two developers are working on the same project, they can each work in their own environments, without the fear of overwriting each other's changes.
Once a developer has made a change, they can push their changes to a remote repository, where other developers can pull the changes and merge them into their own local repositories. This allows for a workflow where changes can be isolated, tested, and then integrated into the main project.
Version Control
Git's version control capabilities are its most obvious feature. Every time a change is made and committed, Git creates a new commit object in the Git repository. This object contains a pointer to the snapshot of the content that was staged, the author who made the change, and the commit message that explains the change.
This means that you can easily see what changes were made, when they were made, and by whom, making it easy to track the progress of a project and to find and fix bugs. Additionally, because every commit has a unique identifier, it's easy to roll back to previous versions of a project if a bug is found.
Conclusion
Git is a powerful, distributed version control system that allows for efficient and robust handling of projects of any size. Its architecture and workflow support a distributed development environment, and its commands provide a rich set of functionality for managing and manipulating repositories.
Whether you're a solo developer working on a small project, or part of a large team working on a major software development, Git is an essential tool in your development workflow. With its powerful features and efficient design, Git has truly changed the landscape of version control systems.