The .git Folder: Complete Project History

A single folder contains everything needed to reconstruct your entire project history.

Running git init creates the hidden .git directory, which stores code history, branches, commits, and configuration.

Practical application: Copy only the .git folder to another machine and run git checkout to restore your complete project.

.git Directory Structure

text.git/
├── objects/     # File content and history storage
├── refs/        # Branch and tag references
├── index        # Staging area snapshot
├── HEAD         # Current branch pointer
└── config       # Repository configuration

The objects/ directory stores all content as compressed, hashed objects.

Git Objects

Blob: File Content Storage

A blob represents the raw content of a single file, independent of its name or path.

Key characteristics:

• Stores only file data (not filename or path)

• Identical content across files shares one blob

• Created during git add

texthello.txt (version 1) → blob abc123
identical.txt         → blob abc123 (shared)
hello.txt (modified)  → blob def456

Tree: Directory Structure

A tree represents a directory and its contents, mapping project structure.

Tree contents:

• File names and permissions

• Directory names

• References to blobs or child trees

textproject-root (tree xyz789)
├── src/ (tree uvw123)
│   └── app.component.ts (blob abc123)
└── styles.css (blob def456)

Commit: Labeled Project Snapshot

A commit captures a complete project state with metadata.

Commit structure:

• Reference to root tree

• Parent commit reference(s)

• Author name and timestamp

• Commit message

textCommit feedface (2026-01-10)
├── Tree: xyz789
├── Parent: cafebabe
├── Author: Your Name
└── Message: "Implement login feature"

Branches are simply references pointing to commit hashes:

textrefs/heads/main → feedface
refs/heads/feature → deadbeef

The git add and git commit Workflow

 Modify app.js
2. git add app.js
   ↓ Creates blob abc123 → .git/objects/12/abc123
   ↓ Updates staging index
3. git commit -m "Add login feature"
   ↓ Creates tree xyz789 (directory structure)
   ↓ Creates commit feedface (project snapshot)
   ↓ Updates main branch reference

Commit chain visualization:

text∅ → commit1(tree1) → commit2(tree2) → main@HEAD(tree3)

Space Efficiency: Content Deduplication

textNaive approach: 1000 commits × 100 files = 100,000 files
Git reality: ~500 unique blobs (incremental changes)

Deduplication occurs across:

• Unchanged files across commits

• Identical files across branches

• Duplicate content across projects

Content Addressing with SHA-1 Hashes

Every Git object uses a 40-character SHA-1 hash derived from its content.

textIdentical content → Identical hash
Single character change → Completely different hash

Benefits:

• Integrity: Tampering invalidates all dependent objects

• Deduplication: Automatic content sharing

• Universality: Object references work across repositories

Storage Organization

text.git/objects/
├── 12/              # Objects with hash prefix "12"
│   └── abc123...    # app.js blob
├── ab/
│   └── def456...    # styles.css blob
└── pack/            # Compressed object bundles