Git Hooks Deep Dive

What you will learn

• Understand the core purpose of Git Hooks Deep Dive
• Master the basic usage and common options of Git Hooks Deep Dive
• Understand Git Hooks types, lifecycle, sharing mechanisms, and CI/CD integration practices.
• Understand key concepts: Overview
• Know when to use this feature and when to avoid it

Start with a problem

You've encountered a conceptual question while using Git — you roughly know what it means, but you're not entirely sure about its precise definition and boundaries.

Overview

Git Hooks are custom scripts triggered at key points during Git operations. They're not built-in Git features but leverage Git's event notification mechanism to run external programs.

Hook Lifecycle

flowchart LR
  subgraph Local
    A[pre-commit] --> B[prepare-commit-msg]
    B --> C[commit-msg]
    C --> D[post-commit]
  end
  subgraph Push
    D --> E[pre-push]
  end
  subgraph Remote
    E --> F[pre-receive]
    F --> G[update]
    G --> H[post-receive]
  end

Core Hooks

Client-Side Hooks

Server-Side Hooks

Practical Hook Examples

pre-commit: Code Quality

#!/bin/bash
# .git/hooks/pre-commit
echo "Running linter..."
npm run lint
if [ $? -ne 0 ]; then
  echo "Lint failed. Commit aborted."
  exit 1
fi

commit-msg: Message Convention

#!/bin/bash
# .git/hooks/commit-msg
PATTERN="^(feat|fix|docs|style|refactor|test|chore|ci)(\(.+\))?: .{1,72}"
msg=$(cat "$1")
if ! [[ "$msg" =~ $PATTERN ]]; then
  echo "Error: commit message must match Conventional Commits format"
  echo "  e.g. feat(api): add login endpoint"
  exit 1
fi

pre-push: Protected Branch Check

#!/bin/bash
# .git/hooks/pre-push
protected_branches="main master develop"
while read local_ref local_sha remote_ref remote_sha; do
  for branch in $protected_branches; do
    if [[ "$remote_ref" == "refs/heads/$branch" ]]; then
      echo "Error: pushing to $branch is not allowed via hook"
      exit 1
    fi
  done
done
exit 0

Sharing Hooks

Method 1: In-Repository (Recommended)

# Project structure
my-repo/
├── .githooks/
│   ├── pre-commit
│   └── commit-msg
└── .gitignore

# Configure custom hooks directory
git config core.hooksPath .githooks

Method 2: Global Hooks

# Create global hooks directory
mkdir -p ~/.git-hooks
git config --global core.hooksPath ~/.git-hooks

Method 3: husky (Node.js Projects)

npx husky init

# .husky/pre-commit
npx lint-staged

CI Integration

# GitHub Actions
jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: npm ci
      - name: Check commit messages
        run: |
          git log --format=%s -1 | grep -E '^(feat|fix|docs)'

Security Notes

1. Server-side hooks first: Client hooks can be bypassed (git commit --no-verify)
2. Don't rely on client hooks for security: Server-side pre-receive is the real defense
3. Hook script permissions: Ensure hooks have execute permission (chmod +x)
4. Performance impact: Complex hooks can significantly slow Git operations

Try it yourself

1. Practice the git-hooks-deep command in a test repository and observe state changes before and after
2. Experiment with different options and compare the output differences
3. Simulate a real scenario where you would need to use this, and walk through the full process

Continue Learning

1. concepts/git-hooks — Git Hooks basics
2. workflows/pre-commit-hook-workflow — Pre-commit hook workflow
3. concepts/git-lfs-deep — Git LFS deep dive

Further reading

Keep going on the same topic:

• Git History Explained
• Git Hooks: Automating Git Workflows
• The Complete Guide to .gitignore