Git Basics

Introduction

Git: distributed version control system. Created by Linus Torvalds in 2005 for Linux kernel development. Tracks changes, enables collaboration, preserves history. Core to modern software engineering. Lightweight, fast, scalable.

"Git is a tool that every developer should master for efficient source code management." -- Scott Chacon

Version Control Concepts

Definition

Version control: management of changes to documents, programs, or information. Tracks modifications, enables rollback, branches, merges.

Types

Centralized (e.g., SVN): single server repository. Distributed (e.g., Git): every user has full copy.

Benefits

History tracking, collaboration, parallel development, conflict resolution, audit trails.

Git Architecture

Data Model

Snapshot-based: stores file tree snapshots, not diffs. Each commit points to a tree object representing file states.

Objects

Four object types: blob (file content), tree (directory), commit (metadata + tree), tag (annotated reference).

References

Branches and tags are refs pointing to commits. HEAD points to current branch or commit.

Storage

Objects stored in .git/objects as compressed files. Index tracks staged changes.

Repositories

Local Repository

Full copy of project, including history. Created via git init or git clone.

Remote Repository

Shared central repository for collaboration. Hosted on servers (GitHub, GitLab, Bitbucket).

Working Directory

Checked-out files for editing. Changes staged before committing.

Repository Structure

.git folder contains metadata, objects, refs, config.

Commits

Definition

Commit: immutable snapshot of project state with metadata (author, date, message).

Commit Hash

SHA-1 hash uniquely identifies commit. Ensures integrity.

Creating Commits

Stage changes with git add, then commit with git commit.

Commit Messages

Brief, descriptive, imperative mood recommended.

Branching

Concept

Branch: movable pointer to a commit. Enables parallel development.

Creating Branches

git branch <name> creates branch. git checkout <name> switches.

Branching Model

Common models: Git Flow, GitHub Flow, trunk-based development.

Branch Lifecycle

Create, develop, merge, delete.

Merging

Purpose

Combine changes from different branches into one.

Types

Fast-forward: branch linear, no new commit. Recursive: creates merge commit.

Conflict Resolution

Conflicts: overlapping changes. Resolved manually or with tools.

Merge Strategies

Recursive, octopus, ours, theirs.

Working with Remote Repositories

Remote Setup

git remote add <name> <url> links local repo to remote.

Fetching and Pulling

git fetch downloads changes. git pull fetches + merges automatically.

Pushing

git push uploads local commits to remote branches.

Tracking Branches

Local branches can track remote branches for synchronization.

Common Git Commands

Initialization & Cloning

git init, git clone <repo_url>

Staging & Committing

git add <file>, git commit -m "message"

Branching & Merging

git branch, git checkout, git merge

Remote Operations

git remote, git fetch, git pull, git push

Status & Logs

git status, git log, git diff

Workflows

Centralized Workflow

Single shared branch. Simple but limited concurrency.

Feature Branch Workflow

Isolated feature branches merged back to main. Supports parallel work.

Git Flow

Defines strict roles for branches: master, develop, feature, release, hotfix.

Forking Workflow

Fork repos for independent development, submit pull requests.

Best Practices

Commit Often

Small, focused commits improve history clarity.

Write Clear Messages

Use imperative mood, summarize intent, reference issues.

Use Branches

Isolate features or fixes to avoid conflicts.

Regularly Sync with Remote

Fetch and merge frequently to reduce conflicts.

Review Before Merge

Code reviews maintain quality and knowledge sharing.

Troubleshooting

Merge Conflicts

Detected when overlapping changes occur. Resolve by editing conflicted files and committing resolutions.

Detached HEAD

HEAD points to a commit, not a branch. To fix, checkout a branch or create a new one.

Undoing Changes

git checkout to discard local changes; git reset to unstage; git revert to create new commit undoing changes.

Recovering Lost Commits

git reflog tracks HEAD moves; can recover commits using reflog hashes.

git refloggit checkout <commit_hash>git branch recovered-branch

References

• S. Chacon, B. Straub, Pro Git, Apress, 2014, pp. 1-500.
• J. Loeliger, M. McCullough, Version Control with Git, O'Reilly Media, 2012, pp. 1-400.
• L. Torvalds, Git Source Code Management, Linux Foundation, 2005.
• M. Duvall, A. Matyas, A. Glover, Continuous Integration: Improving Software Quality and Reducing Risk, Addison-Wesley, 2007, pp. 1-350.
• K. Beck, Test Driven Development: By Example, Addison-Wesley, 2003, pp. 1-240.