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git hooks

Description:
Scripts that run automatically on Git events. Customize and automate your workflow with pre-commit, post-commit, pre-push, and other hooks.

Hook Types:

# Client-side hooks
pre-commit          # Before commit is created
prepare-commit-msg  # Before commit message editor
commit-msg          # After commit message entered
post-commit         # After commit is created
pre-rebase          # Before rebase starts
post-checkout       # After checkout
post-merge          # After merge
pre-push            # Before push to remote

# Server-side hooks
pre-receive         # Before refs updated
update              # Once per ref being updated
post-receive        # After all refs updated

Location:

.git/hooks/
├── pre-commit.sample
├── pre-push.sample
├── commit-msg.sample
└── ...

Creating a Hook:

# 1. Navigate to hooks directory
cd .git/hooks

# 2. Create hook file (without .sample)
touch pre-commit

# 3. Make executable
chmod +x pre-commit

# 4. Add script content

Example Hooks:

Pre-Commit Hook (Run Tests):

#!/bin/bash
# .git/hooks/pre-commit

echo "Running tests before commit..."

# Run tests
npm test

# Check exit code
if [ $? -ne 0 ]; then
    echo "Tests failed. Commit aborted."
    exit 1
fi

echo "Tests passed. Proceeding with commit."
exit 0

Pre-Commit Hook (Code Linting):

#!/bin/bash
# .git/hooks/pre-commit

echo "Running linter..."

# Run linter on staged files
npm run lint-staged

if [ $? -ne 0 ]; then
    echo "Linting failed. Please fix errors."
    exit 1
fi

echo "Linting passed."
exit 0

Commit-Msg Hook (Enforce Format):

#!/bin/bash
# .git/hooks/commit-msg

commit_msg=$(cat "$1")

# Check for conventional commit format
if ! echo "$commit_msg" | grep -qE "^(feat|fix|docs|style|refactor|test|chore)(\(.+\))?: .+"; then
    echo "Commit message must follow format: type(scope): message"
    echo "Types: feat, fix, docs, style, refactor, test, chore"
    exit 1
fi

echo "Commit message format valid."
exit 0

Pre-Push Hook (Prevent Force Push):

#!/bin/bash
# .git/hooks/pre-push

protected_branches=("main" "master" "production")

while read local_ref local_sha remote_ref remote_sha
do
    for branch in "${protected_branches[@]}"
    do
        if [[ "$remote_ref" == *"$branch" ]]; then
            if [ "$remote_sha" != "0000000000000000000000000000000000000000" ]; then
                echo "Direct push to $branch is not allowed!"
                exit 1
            fi
        fi
    done
done

echo "Push allowed."
exit 0

Popular Hook Use Cases:

1. Code Quality:

   • Run linters (ESLint, Pylint, etc.)
   • Format code (Prettier, Black, etc.)
   • Check code style

2. Testing:

   • Run unit tests
   • Run integration tests
   • Check test coverage

3. Security:

   • Scan for secrets/credentials
   • Check for vulnerable dependencies
   • Verify commit signatures

4. Documentation:

   • Generate documentation
   • Update changelog
   • Check documentation coverage

5. Workflow Enforcement:

   • Enforce commit message format
   • Prevent force pushes to protected branches
   • Require issue references

Using Hook Managers:

Husky (Node.js):

# Install Husky
npm install --save-dev husky

# Initialize
npx husky install

# Add pre-commit hook
npx husky add .husky/pre-commit "npm test"

Pre-commit Framework (Python):

# Install pre-commit
pip install pre-commit

# Create .pre-commit-config.yaml
pre-commit install

Bypassing Hooks:

# Skip hooks for one commit
git commit --no-verify -m "Emergency fix"

# Skip pre-push hook
git push --no-verify

Common Errors:

• hint: The '.git/hooks/pre-commit' hook was ignored → Solution: Make hook executable: chmod +x .git/hooks/pre-commit
• Hook doesn't run → Solution: Verify filename (no .sample extension) and executable permission

Pro Tips:

• Keep hooks fast - slow hooks frustrate developers
• Share hooks via .githooks/ directory, symlink to .git/hooks/
• Use hook managers (Husky, pre-commit) for team consistency
• Exit with code 0 (success) or 1 (failure) to control Git operation
• Use --no-verify only for emergencies
• Hooks are local - not pushed to remote (except via hook managers)

Related Commands:

• git commit – Triggers commit hooks
• git push – Triggers push hooks
• git config – Configure hook paths

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Advanced Workflows

Interactive Rebase

# Rewrite last 3 commits
git rebase -i HEAD~3

# In editor, choose action:
# pick = use commit
# reword = change commit message
# edit = modify commit
# squash = combine with previous
# fixup = combine, discard message
# drop = remove commit

Cherry-pick Multiple Commits

# Pick range of commits
git cherry-pick abc123^..def456

# Pick multiple non-consecutive commits
git cherry-pick abc123 def456 ghi789

Archive Repository

# Create tarball of repository
git archive --format=tar --output=project.tar HEAD

# Create zip file
git archive --format=zip --output=project.zip HEAD

# Archive specific branch
git archive --format=tar --output=release.tar v1.0

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See Also

• Git Basics →
• Git Branching →
• Git Workflows →
• Git FAQ →
• Quick Reference →

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