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Git Introduction

What is Git?​

Git logo

Git is a distributed version control system that helps developers track changes in their code. Created by Linus Torvalds in 2005 (the same person who developed Linux), Git has become the industry standard for version control.

Unlike older version control systems, Git:

  • Works offline
  • Is blazingly fast
  • Supports non-linear development (branching and merging)
  • Provides complete history and full version-tracking capabilities
  • Ensures data integrity

Why Learn Git?​

Whether you're a solo developer or part of a large team, Git offers numerous benefits:

  • Track changes: Keep a complete history of your project
  • Experiment safely: Create branches to try new ideas without affecting the main codebase
  • Collaborate: Work seamlessly with others on the same project
  • Backup: Store your code in remote repositories (like GitHub, GitLab, or Bitbucket)
  • Employability: Git skills are expected in almost all programming jobs

Git vs. GitHub: Understanding the Difference​

Many beginners confuse Git and GitHub. Let's clarify:

  • Git: The version control system you install and run on your local machine
  • GitHub: A web-based hosting service for Git repositories that adds collaboration features

Think of Git as the tool and GitHub as a service built around that tool.

Getting Started with Git​

Installation​

Before using Git, you need to install it on your computer.

For Windows:​

  1. Download the installer from git-scm.com
  2. Run the installer and follow the default options

To verify installation, open Command Prompt and type:

bash
git --version

For macOS:​

If you have Homebrew installed:

bash
brew install git

Or download from git-scm.com

For Linux (Ubuntu/Debian):​

bash
sudo apt-get update
sudo apt-get install git

Basic Configuration​

After installation, you should configure Git with your identity:

bash
git config --global user.name "Your Name"
git config --global user.email "your.email@example.com"

These details will be associated with any commits you make.

Core Git Concepts​

Repositories​

A Git repository (or "repo") is a collection of files and the history of changes made to those files. It contains a special .git directory that stores all the version control information.

Creating a New Repository​

To create a new Git repository:

  1. Create a new directory for your project
  2. Navigate to that directory in your terminal
  3. Initialize the repository with the following command:
bash
mkdir my-project
cd my-project
git init

You should see a message like:

Initialized empty Git repository in /path/to/my-project/.git/

The Three States of Git​

Files in your working directory can exist in three states:

  1. Modified: You've changed the file but haven't committed it yet
  2. Staged: You've marked the modified file to go into your next commit
  3. Committed: The file is safely stored in your Git database

The Basic Git Workflow​

Here's the fundamental workflow you'll use:

  1. Modify files in your working directory
  2. Stage the files, adding snapshots to your staging area
  3. Commit the files, which stores the snapshots permanently in your Git repository

Let's walk through this process with an example:

bash
# Create a simple HTML file
echo "<html><body><h1>Hello Git World!</h1></body></html>" > index.html

# Check the status of your repository
git status

Output:

On branch master

No commits yet

Untracked files:
  (use "git add <file>..." to include in what will be committed)
        index.html

nothing added to commit but untracked files present (use "git add" to track)

Now let's stage this file:

bash
git add index.html
git status

Output:

On branch master

No commits yet

Changes to be committed:
  (use "git rm --cached <file>..." to unstage)
        new file:   index.html

Finally, let's commit the staged changes:

bash
git commit -m "Add index.html with initial content"

Output:

[master (root-commit) f344d76] Add index.html with initial content
 1 file changed, 1 insertion(+)
 create mode 100644 index.html

Congratulations! You've made your first Git commit.

Viewing Your Commit History​

To see your commit history:

bash
git log

Output:

commit f344d76e8aff6a9e9abbb466bacc4a3a627d9c67 (HEAD -> master)
Author: Your Name <your.email@example.com>
Date:   Mon Mar 14 10:00:00 2025

    Add index.html with initial content

Making Changes and Tracking Them​

Let's modify our file and see how Git tracks changes:

bash
# Edit the file
echo "<html><body><h1>Hello Git World!</h1><p>Learning Git is fun!</p></body></html>" > index.html

# Check status
git status

Output:

On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   index.html

no changes added to commit (use "git add" and/or "git commit -a")

Let's stage and commit these changes:

bash
git add index.html
git commit -m "Add paragraph about learning Git"

Output:

[master ab74627] Add paragraph about learning Git
 1 file changed, 1 insertion(+), 1 deletion(-)

Viewing Differences​

To see what changes you've made before staging:

bash
git diff

To see what's staged and will be committed:

bash
git diff --staged

Understanding Git Branches​

Branches allow you to diverge from the main line of development and continue working without messing with the main line.

Creating a Branch​

To create a new branch:

bash
git branch feature-navbar

To switch to that branch:

bash
git checkout feature-navbar

Or do both in one command:

bash
git checkout -b feature-navbar

Working with Branches​

Now that you're on a new branch, any changes you make won't affect the main branch (usually called master or main).

Let's make some changes:

bash
# Edit the file on our feature branch
echo "<html><body><nav>Home | About</nav><h1>Hello Git World!</h1><p>Learning Git is fun!</p></body></html>" > index.html

# Stage and commit the changes
git add index.html
git commit -m "Add simple navigation bar"

To switch back to the main branch:

bash
git checkout master

Notice that our index.html file returns to its previous state without the navigation bar.

Merging Branches​

When you're ready to bring your changes from a feature branch back into the main branch:

bash
# First, make sure you're on the branch you want to merge into (usually master)
git checkout master

# Then merge the feature branch
git merge feature-navbar

If there are no conflicts, Git will automatically create a merge commit.

Remote Repositories​

Remote repositories are versions of your project hosted on the internet or network. They allow you to:

  1. Backup your code
  2. Collaborate with others
  3. Deploy your applications

Adding a Remote Repository​

To connect your local repository to a remote repository (like on GitHub):

bash
git remote add origin https://github.com/username/repository-name.git

Pushing to a Remote Repository​

To push your commits to the remote repository:

bash
git push -u origin master

The -u flag sets up tracking, so in the future you can simply use git push.

Cloning a Repository​

To create a local copy of a remote repository:

bash
git clone https://github.com/username/repository-name.git

This creates a new directory with the repository name, initializes a .git directory, pulls all the data from the remote repository, and checks out the latest version.

Pulling Changes​

To get updates from a remote repository:

bash
git pull

This fetches changes from the remote and merges them into your current branch.

Common Git Commands Summary​

Here's a quick reference of the most commonly used Git commands:

CommandDescription
git initCreate a new Git repository
git cloneClone a repository
git addAdd files to staging area
git commitCommit changes
git statusShow repository status
git logView commit history
git branchList, create, or delete branches
git checkoutSwitch branches or restore files
git mergeMerge branches
git pullFetch and merge changes
git pushUpdate remote repository
git remoteManage remote repositories

Best Practices for Using Git​

To make the most of Git, follow these practices:

  1. Commit often: Make small, focused commits rather than large, sweeping changes
  2. Write meaningful commit messages: Explain what and why, not how
  3. Use branches: Create a new branch for each feature or bug fix
  4. Pull before pushing: Always pull changes before pushing to avoid conflicts
  5. Review changes before committing: Use git diff and git status to verify changes

Summary​

Git is a powerful, distributed version control system that helps you track changes, collaborate with others, and maintain the history of your projects. In this introduction, we've covered:

  • What Git is and why it's valuable
  • How to set up Git
  • Basic Git workflow with committing changes
  • Working with branches
  • Connecting to remote repositories

Learning Git may seem challenging at first, but it becomes intuitive with practice. The skills you develop will serve you throughout your programming career.

Additional Resources​

To continue learning Git, consider these resources:

Practice Exercises​

  1. Create a new Git repository for a personal project
  2. Make several commits with meaningful messages
  3. Create a branch, make changes, and merge it back to the main branch
  4. Create a GitHub account and push your repository to it
  5. Clone an open-source repository and explore its history with git log

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