Git & GitHub — Version Control from Basics to Advanced

How Git stores history, the daily commands, branching and merging, rebase, resolving conflicts, remotes and pull requests, branching strategies (GitFlow, trunk-based), undoing mistakes, tags and releases, hooks and the Git questions asked in every developer interview.

What it is & where it is used

Git is a distributed version control system: every developer has the full history locally, commits offline, and synchronises with a shared remote (GitHub, Azure Repos, GitLab, Bitbucket).

Term	Meaning
Repository (repo)	The project folder plus its full history (`.git` directory)
Commit	A snapshot of the project with author, message and parent commit(s)
Branch	A movable pointer to a commit
HEAD	Pointer to what you have checked out (usually a branch)
Working tree / staging area (index) / repository	Edited files → `git add` → `git commit`
Remote	Another copy of the repo, usually `origin`
Pull request (PR) / merge request	A request to merge a branch, with review and CI checks

Git vs older tools: TFVC and SVN are centralised (one server holds history, you check out files); Git is distributed, branching is cheap and merging is fast.

Versions & history

Year	Milestone
2005	Linus Torvalds creates Git for Linux kernel development
2008	GitHub launches
2014	Git 2.0 — `push.default=simple`
2018	Microsoft acquires GitHub; Azure Repos (Azure DevOps) supports Git
2019	Git 2.23 — `git switch` and `git restore` split the many jobs of `checkout`
2020	GitHub and Git default branch name moves to `main` (configurable via `init.defaultBranch`)
2020+	`git sparse-checkout`, partial clone, `git maintenance` for big repos
2023	Git 2.42+ — SHA-256 repositories maturing
2025	Git 2.5x series; Git 3.0 planned (SHA-256 default, `main` default)

Lifecycle

File states: untracked → (git add) → staged → (git commit) → committed → (edit) → modified → staged again …

Typical feature workflow:

git switch main && git pull — start from the latest main.
git switch -c feature/ORD-123-order-search — create a branch.
Edit, git add -p, git commit -m "Add order search endpoint" — small, focused commits.
git push -u origin feature/ORD-123-order-search.
Open a pull request; CI runs build + tests; reviewers comment; you push fixes.
Update with main if needed (git pull --rebase origin main or merge main in).
Merge (merge commit, squash or rebase-merge per team policy); delete the branch.
Release: tag (v2.3.0) and deploy through CD.

Tools used to develop

CLI: git (Git for Windows includes Git Bash and Git Credential Manager).
IDEs: Visual Studio Git window, VS Code Source Control + GitLens, JetBrains Rider.
GUIs: GitHub Desktop, Sourcetree, GitKraken, Fork, TortoiseGit.
Hosting: GitHub (PRs, Actions, Codespaces), Azure Repos (PRs, branch policies), GitLab, Bitbucket.
Quality: pre-commit hooks, Husky (JS), commitlint, .gitattributes, .gitignore templates, Git LFS for big binaries.