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How Version Control Actually Works: A Practical Git Deep Dive

gitversion-controlsoftware-engineering

Introduction

Most developers use Git daily, yet many treat it as a collection of memorized commands rather than a system they truly understand. This often leads to confusion when things go wrong—merge conflicts, detached HEAD states, or lost commits.

This post explains how Git actually works under the hood, focusing on practical concepts rather than surface-level commands.

What Problem Does Version Control Solve?

Version control systems exist to solve three core problems:

  1. Tracking changes over time
  2. Enabling collaboration between developers
  3. Allowing safe experimentation and rollback

Git approaches these problems very differently from traditional file-based version control systems.

Git Is Not a File Diff Tool

A common misconception is that Git stores “differences between files.”
In reality, Git stores snapshots of your project.

Each commit represents the complete state of the project at a specific point in time. Git efficiently reuses unchanged files internally, but conceptually, every commit is a full snapshot.

This design is what makes branching and merging fast and reliable.

The Three States of Git

Git operates around three main areas:

  1. Working Directory – Your actual files
  2. Staging Area (Index) – A preparation area for the next commit
  3. Repository (HEAD) – The committed history
Working Directory → Staging Area → Repository

Understanding this flow is critical to using Git confidently.

What a Commit Really Is

A Git commit is not just a message—it is an object with:

  • A snapshot of the project
  • A reference to its parent commit(s)
  • Author and timestamp metadata
  • A commit message

Each commit points to its parent, forming a directed acyclic graph (DAG), not a simple linear history.

Branches Are Just Pointers

Branches in Git are lightweight references to commits.

main → a1b2c3
feature-x → d4e5f6

Creating a branch does not copy files. It simply creates a new pointer. This is why branching in Git is fast and encouraged.

The special pointer HEAD tells Git which branch (or commit) you are currently on.

Merging vs Rebasing (Conceptually)

Merge

  • Combines histories
  • Preserves context
  • Creates a merge commit
git merge feature-x

Rebase

  • Rewrites history
  • Creates a linear timeline
  • Changes commit hashes
git rebase main

Rule of thumb: Rebase local work, merge shared work.

What Happens During a Merge Conflict?

A merge conflict occurs when Git cannot automatically reconcile changes because the same lines were modified differently.

Git does not guess. It stops and asks you to decide.

Conflict markers look like this:

<<<<<<< HEAD
current branch code
=======
incoming branch code
>>>>>>> feature-x

Resolving conflicts is not a failure—it is a normal part of collaborative development.

Git Is Content-Addressed

Git identifies objects using hashes (SHA-1 or SHA-256 in newer versions).

This means:

  • Data integrity is guaranteed
  • Identical content is stored once
  • History is tamper-evident

Everything—commits, trees, blobs—is referenced by its hash.

Why Commits Are (Almost) Never Lost

Even when you:

  • Delete a branch
  • Reset hard
  • Checkout a previous commit

Git usually keeps objects until garbage collection runs.

Tools like git reflog allow you to recover “lost” commits:

git reflog

Understanding this dramatically reduces fear when experimenting.

Local vs Remote Repositories

A remote repository (like GitHub) is just another Git repository.

Commands like:

git fetch
git pull
git push

move commit objects and update pointers. There is no magic—only data transfer and reference updates.

Best Practices Backed by Understanding

Once you understand how Git works, best practices become logical:

  • Commit small, logical changes
  • Write meaningful commit messages
  • Avoid rewriting public history
  • Use branches aggressively
  • Review diffs before staging

These are not rules—they are consequences of Git’s design.

Conclusion

Git is powerful not because it has many commands, but because of its internal model: snapshots, pointers, and immutable history. Developers who understand this model work faster, make fewer mistakes, and recover confidently when things go wrong.

Mastering Git is less about memorization and more about mental models.

Final Takeaway

If you ever feel “stuck” in Git, stop typing commands and ask:

What pointer am I on, and what commit does it reference?

That single question solves most Git problems.

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