📚 Pre-commit Deep Learning Guide

A comprehensive guide to mastering pre-commit hooks for automated code quality checks

---

📖 Table of Contents

1. What is Pre-commit?
2. Learning Roadmap
3. Core Concepts
4. Configuration Reference
5. Built-in Hooks
6. Language-Specific Hooks
7. Custom Hooks
8. Best Practices
9. Integration Strategies
10. Troubleshooting
11. Resources

---

🎯 What is Pre-commit?

Pre-commit is a framework for managing and maintaining multi-language pre-commit hooks.

The Problem

Without pre-commit:

# Developer commits bad code
git commit -m "Add feature"

# CI fails 10 minutes later
❌ Linting failed
❌ Tests failed
❌ Formatting check failed

# Developer fixes and commits again
git commit -m "Fix linting"

The Solution

With pre-commit:

# Developer tries to commit
git commit -m "Add feature"

# Pre-commit runs automatically BEFORE commit
⏳ Running hooks...
❌ trailing-whitespace......Failed
❌ eslint..................Failed

# Commit blocked! Fix issues first.
# After fixing:
✅ All hooks passed!
[main abc123] Add feature

Key Benefits

✅ Catch issues early: Before they reach CI/CD
✅ Save time: Fix problems locally, not in CI
✅ Enforce standards: Automatically check code quality
✅ Multi-language: Works with Python, JS, Go, Rust, etc.
✅ Easy setup: Simple YAML configuration
✅ Team consistency: Everyone uses same checks

---

🧩 Core Concepts

1. Git Hooks Overview

Git has built-in hooks for various events:

.git/hooks/
├── pre-commit         # Before commit
├── prepare-commit-msg # Before commit message editor
├── commit-msg         # After commit message entered
├── post-commit        # After commit completed
├── pre-push           # Before push
├── pre-rebase         # Before rebase
└── ... (many more)

Problem with raw Git hooks:

• Not version-controlled (in .git/ directory)
• Hard to share with team
• Language-specific (shell scripts)
• No easy way to manage dependencies

2. Pre-commit Framework

Pre-commit solves these problems:

# .pre-commit-config.yaml (version-controlled!)
repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      - id: trailing-whitespace
      - id: end-of-file-fixer

How it works:

1. You run: git commit
           ↓
2. Git triggers: .git/hooks/pre-commit
           ↓
3. Pre-commit reads: .pre-commit-config.yaml
           ↓
4. Pre-commit runs: All configured hooks
           ↓
5. If all pass: Commit succeeds ✅
   If any fail: Commit blocked ❌

3. Hook Repository Structure

A hook repository contains:

hook-repo/
├── .pre-commit-hooks.yaml    # Hook definitions
├── setup.py or package.json  # Dependencies
└── scripts/
    ├── check-something.py
    └── fix-something.sh

.pre-commit-hooks.yaml example:

- id: trailing-whitespace
  name: Trim Trailing Whitespace
  entry: trailing-whitespace-fixer
  language: python
  types: [text]

4. Hook Execution Flow

File staged for commit
       ↓
Filter by file types/patterns
       ↓
Run hook entry point
       ↓
Check exit code
       ↓
Exit 0: Pass ✅ | Non-zero: Fail ❌
       ↓
All hooks pass? → Commit | Any fail? → Block

5. File Filtering

Pre-commit automatically filters files:

- id: eslint
  types: [javascript]      # Only .js files
  exclude: '^vendor/'      # Skip vendor/
  files: '^src/'           # Only src/

Filter precedence: types → files → exclude

---

📋 Configuration Reference

Basic Structure

# Minimum version of pre-commit required
minimum_pre_commit_version: '2.15.0'

# Default settings for all repos
default_install_hook_types: [pre-commit, pre-push]
default_stages: [commit, push]

# Exclude files globally
exclude: '^(vendor/|node_modules/|\.min\.js$)'

# Fail fast (stop on first failure)
fail_fast: false

# Hook repositories
repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      - id: trailing-whitespace

Repository Configuration

repos:
  # Remote repository
  - repo: https://github.com/psf/black
    rev: 23.11.0
    hooks:
      - id: black
        
  # Local hooks (in your repo)
  - repo: local
    hooks:
      - id: my-custom-script
        name: My Custom Check
        entry: ./scripts/check.sh
        language: script
        
  # Meta hooks (pre-commit itself)
  - repo: meta
    hooks:
      - id: check-hooks-apply
      - id: check-useless-excludes

Hook Configuration

hooks:
  - id: black
    # Override hook name
    name: Format Python with Black
    
    # Additional arguments
    args: [--line-length=88, --target-version=py311]
    
    # File filtering
    types: [python]
    types_or: [python, pyi]
    exclude: '^tests/fixtures/'
    files: '^src/.*\.py$'
    
    # Execution settings
    language: python
    language_version: python3.11
    pass_filenames: true
    require_serial: false
    
    # Stages to run in
    stages: [commit, push]
    
    # Always run (even if no files match)
    always_run: false
    
    # Verbose output
    verbose: false
    
    # Additional dependencies
    additional_dependencies:
      - tokenize-rt==5.2.0

Language Types

language: system        # Use system-installed binary
language: python        # Create Python virtualenv
language: node          # Create Node.js environment
language: ruby          # Create Ruby environment
language: golang        # Create Go environment
language: rust          # Create Rust environment
language: docker        # Run in Docker container
language: script        # Run as shell script
language: fail          # Always fail (for testing)

File Type Filtering

types: [file]              # Any file
types: [text]              # Text files only
types: [python]            # Python files
types: [javascript]        # JavaScript files
types: [json]              # JSON files
types: [yaml]              # YAML files
types: [markdown]          # Markdown files
types: [shell]             # Shell scripts

# Custom types
types_or: [python, pyi, jupyter]
exclude_types: [binary]

Stages

stages:
  - commit              # Pre-commit (default)
  - merge-commit        # Pre-merge-commit
  - push                # Pre-push
  - prepare-commit-msg  # Prepare commit message
  - commit-msg          # Commit message hook
  - post-checkout       # Post-checkout
  - post-commit         # Post-commit
  - post-merge          # Post-merge
  - post-rewrite        # Post-rewrite
  - manual              # Only when explicitly run

---

🔧 Built-in Hooks

Essential Pre-commit Hooks

repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      # File formatting
      - id: trailing-whitespace
        name: Trim trailing whitespace
        
      - id: end-of-file-fixer
        name: Fix end of files
        
      - id: mixed-line-ending
        args: [--fix=lf]
        
      # File checks
      - id: check-added-large-files
        args: [--maxkb=1000]
        
      - id: check-merge-conflict
      - id: check-symlinks
      - id: destroyed-symlinks
      
      # Syntax validation
      - id: check-yaml
        args: [--safe]
        
      - id: check-json
      - id: check-toml
      - id: check-xml
      
      # Security
      - id: detect-private-key
      - id: detect-aws-credentials
        args: [--allow-missing-credentials]
        
      # Python-specific
      - id: check-ast
      - id: check-builtin-literals
      - id: check-docstring-first
      - id: debug-statements
      - id: name-tests-test
        args: [--pytest-test-first]
        
      # Misc
      - id: check-case-conflict
      - id: check-executables-have-shebangs
      - id: check-shebang-scripts-are-executable
      - id: fix-byte-order-marker

Hook Descriptions

Hook ID	What it Does	Auto-fix?
trailing-whitespace	Remove spaces at end of lines	✅
end-of-file-fixer	Ensure files end with newline	✅
check-yaml	Validate YAML syntax	❌
check-json	Validate JSON syntax	❌
check-merge-conflict	Detect merge conflict markers	❌
check-added-large-files	Prevent large files (default 500KB)	❌
detect-private-key	Find private keys in code	❌
mixed-line-ending	Fix CRLF/LF inconsistencies	✅
check-ast	Verify Python syntax	❌
debug-statements	Find breakpoint(), pdb	❌

---

🐍 Language-Specific Hooks

Python

repos:
  # Black - Code formatter
  - repo: https://github.com/psf/black
    rev: 23.11.0
    hooks:
      - id: black
        args: [--line-length=88]
        
  # isort - Import sorter
  - repo: https://github.com/PyCQA/isort
    rev: 5.12.0
    hooks:
      - id: isort
        args: [--profile=black]
        
  # Ruff - Fast linter
  - repo: https://github.com/astral-sh/ruff-pre-commit
    rev: v0.1.6
    hooks:
      - id: ruff
        args: [--fix, --exit-non-zero-on-fix]
      - id: ruff-format
        
  # mypy - Type checking
  - repo: https://github.com/pre-commit/mirrors-mypy
    rev: v1.7.1
    hooks:
      - id: mypy
        additional_dependencies: [types-requests]
        
  # Flake8 - Linter
  - repo: https://github.com/PyCQA/flake8
    rev: 6.1.0
    hooks:
      - id: flake8
        args: [--max-line-length=88]
        
  # Bandit - Security linter
  - repo: https://github.com/PyCQA/bandit
    rev: 1.7.5
    hooks:
      - id: bandit
        args: [-c, pyproject.toml]

JavaScript/TypeScript

repos:
  # ESLint
  - repo: https://github.com/pre-commit/mirrors-eslint
    rev: v8.54.0
    hooks:
      - id: eslint
        files: \.[jt]sx?$
        types: [file]
        additional_dependencies:
          - eslint@8.54.0
          - eslint-config-standard@17.1.0
          - '@typescript-eslint/eslint-plugin@6.12.0'
          - '@typescript-eslint/parser@6.12.0'
          
  # Prettier
  - repo: https://github.com/pre-commit/mirrors-prettier
    rev: v3.1.0
    hooks:
      - id: prettier
        types_or: [javascript, jsx, ts, tsx, json, yaml, markdown]
        
  # TypeScript compiler
  - repo: https://github.com/pre-commit/mirrors-tsc
    rev: v5.3.2
    hooks:
      - id: tsc

Go

repos:
  # gofmt - Formatter
  - repo: https://github.com/dnephin/pre-commit-golang
    rev: v0.5.1
    hooks:
      - id: go-fmt
      - id: go-vet
      - id: go-imports
      - id: go-lint
      - id: go-unit-tests
      
  # golangci-lint
  - repo: https://github.com/golangci/golangci-lint
    rev: v1.55.2
    hooks:
      - id: golangci-lint

Rust

repos:
  - repo: https://github.com/doublify/pre-commit-rust
    rev: v1.0
    hooks:
      - id: fmt
      - id: cargo-check
      - id: clippy

Shell Scripts

repos:
  # ShellCheck
  - repo: https://github.com/shellcheck-py/shellcheck-py
    rev: v0.9.0.6
    hooks:
      - id: shellcheck
        
  # shfmt - Shell formatter
  - repo: https://github.com/scop/pre-commit-shfmt
    rev: v3.7.0-1
    hooks:
      - id: shfmt
        args: [-i, '2', -ci]

Docker

repos:
  # Hadolint - Dockerfile linter
  - repo: https://github.com/hadolint/hadolint
    rev: v2.12.0
    hooks:
      - id: hadolint-docker

Markdown

repos:
  # markdownlint
  - repo: https://github.com/igorshubovych/markdownlint-cli
    rev: v0.37.0
    hooks:
      - id: markdownlint
        args: [--fix]
        
  # markdown-link-check
  - repo: https://github.com/tcort/markdown-link-check
    rev: v3.11.2
    hooks:
      - id: markdown-link-check

---

🛠️ Custom Hooks

Local Hooks

repos:
  - repo: local
    hooks:
      # Shell script
      - id: check-secrets
        name: Check for secrets
        entry: ./scripts/check-secrets.sh
        language: script
        
      # Python script
      - id: custom-validator
        name: Custom validation
        entry: python scripts/validate.py
        language: system
        types: [python]
        
      # Direct command
      - id: no-console-log
        name: Block console.log
        entry: bash -c 'grep -r "console.log" src/ && exit 1 || exit 0'
        language: system
        types: [javascript]
        pass_filenames: false
        
      # Always run hook
      - id: check-api-health
        name: Check API is running
        entry: curl -f http://localhost:8000/health
        language: system
        pass_filenames: false
        always_run: true
        stages: [push]

Creating a Hook Repository

1. Create repository structure:

my-hooks/
├── .pre-commit-hooks.yaml
├── setup.py
└── my_hooks/
    ├── __init__.py
    └── check_something.py

2. Define hooks (.pre-commit-hooks.yaml):

- id: check-api-keys
  name: Check for exposed API keys
  entry: check-api-keys
  language: python
  types: [text]
  
- id: validate-config
  name: Validate configuration files
  entry: validate-config
  language: python
  files: \.(json|yaml|toml)$

3. Implement hook (my_hooks/check_something.py):

#!/usr/bin/env python3
import re
import sys

def check_api_keys(filenames):
    """Check files for exposed API keys."""
    api_key_pattern = re.compile(r'(api[_-]?key|apikey)\s*=\s*["\'][\w-]{20,}["\']', re.IGNORECASE)
    
    errors = []
    for filename in filenames:
        with open(filename, 'r') as f:
            for line_num, line in enumerate(f, 1):
                if api_key_pattern.search(line):
                    errors.append(f"{filename}:{line_num} - Possible API key found")
    
    if errors:
        print("\n".join(errors))
        return 1
    return 0

def main():
    return check_api_keys(sys.argv[1:])

if __name__ == '__main__':
    sys.exit(main())

4. Setup packaging (setup.py):

from setuptools import setup, find_packages

setup(
    name='my-pre-commit-hooks',
    version='1.0.0',
    packages=find_packages(),
    install_requires=[],
    entry_points={
        'console_scripts': [
            'check-api-keys=my_hooks.check_something:main',
        ],
    },
)

5. Use in projects:

repos:
  - repo: https://github.com/yourusername/my-hooks
    rev: v1.0.0
    hooks:
      - id: check-api-keys

---

✅ Best Practices

1. Start Simple, Grow Gradually

# ✅ Good - Start minimal
repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      - id: trailing-whitespace
      - id: end-of-file-fixer
      - id: check-yaml

# ❌ Bad - Too many hooks at once
repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks: # 20+ hooks listed

Approach: Add hooks incrementally, let team adapt.

2. Auto-fix When Possible

# ✅ Good - Auto-fixes
- id: trailing-whitespace    # Fixes automatically
- id: black                  # Formats code
- id: isort                  # Sorts imports

# ⚠️ Only check - requires manual fix
- id: flake8                 # Reports issues
- id: mypy                   # Reports type errors

Balance: Mix auto-fix hooks (fast feedback) with check hooks (enforce quality).

3. Order Hooks Logically

repos:
  # 1. Format code first
  - repo: https://github.com/psf/black
    rev: 23.11.0
    hooks:
      - id: black
      
  # 2. Then sort imports
  - repo: https://github.com/PyCQA/isort
    rev: 5.12.0
    hooks:
      - id: isort
      
  # 3. Finally lint
  - repo: https://github.com/PyCQA/flake8
    rev: 6.1.0
    hooks:
      - id: flake8

Rationale: Formatters change code, run them before linters.

4. Set Appropriate Stages

repos:
  # Fast checks - run on commit
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      - id: trailing-whitespace
        stages: [commit]
        
  # Expensive checks - run on push
  - repo: https://github.com/pre-commit/mirrors-mypy
    rev: v1.7.1
    hooks:
      - id: mypy
        stages: [push]
        
  # Critical checks - run on both
  - repo: https://github.com/PyCQA/bandit
    rev: 1.7.5
    hooks:
      - id: bandit
        stages: [commit, push]

5. Exclude Generated/Vendor Files

# Global exclude
exclude: '^(vendor/|node_modules/|dist/|build/|\.min\.js$)'

# Hook-specific exclude
hooks:
  - id: eslint
    exclude: '^(vendor/|.*\.generated\..*)$'

6. Pin Versions

# ✅ Good - Specific version
- repo: https://github.com/psf/black
  rev: 23.11.0

# ❌ Bad - Floating version
- repo: https://github.com/psf/black
  rev: main

Update regularly:

pre-commit autoupdate

7. Document Your Configuration

# .pre-commit-config.yaml

# This configuration runs automatically before commits.
# To run manually: pre-commit run --all-files
# To update hooks: pre-commit autoupdate
# To skip hooks: git commit --no-verify

repos:
  # Code formatting - auto-fixes files
  - repo: https://github.com/psf/black
    rev: 23.11.0
    hooks:
      - id: black
        # Line length matches flake8 config
        args: [--line-length=88]

8. Use with CI/CD

# .github/workflows/pre-commit.yml
name: Pre-commit

on: [push, pull_request]

jobs:
  pre-commit:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - uses: actions/setup-python@v4
      - uses: pre-commit/action@v3.0.0

Why: Catch issues even if developers skip hooks locally.

---

🔄 Integration Strategies

With Existing Projects

Step 1: Install pre-commit

pip install pre-commit

Step 2: Add minimal config

repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      - id: trailing-whitespace
      - id: end-of-file-fixer

Step 3: Run on all files once

pre-commit run --all-files

Step 4: Fix issues or update config

# Fix issues
git add -u
git commit -m "Apply pre-commit fixes"

# Or exclude problematic files
echo "exclude: '^legacy/'" >> .pre-commit-config.yaml

Step 5: Install for team

pre-commit install

With EditorConfig

# Use both together
repos:
  # EditorConfig validation
  - repo: https://github.com/editorconfig-checker/editorconfig-checker.python
    rev: 2.7.3
    hooks:
      - id: editorconfig-checker
        
  # Pre-commit hooks
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      - id: trailing-whitespace
      - id: end-of-file-fixer

With Prettier + ESLint

repos:
  # Prettier first (formatting)
  - repo: https://github.com/pre-commit/mirrors-prettier
    rev: v3.1.0
    hooks:
      - id: prettier
        types_or: [javascript, jsx, ts, tsx, json, yaml]
        
  # ESLint second (linting)
  - repo: https://github.com/pre-commit/mirrors-eslint
    rev: v8.54.0
    hooks:
      - id: eslint
        files: \.[jt]sx?$
        types: [file]

With Husky (Node.js projects)

Choose one approach:

Option A: Use pre-commit only

{
  "devDependencies": {
    "pre-commit": "^3.5.0"
  }
}

Option B: Use Husky + lint-staged

{
  "husky": {
    "hooks": {
      "pre-commit": "lint-staged"
    }
  },
  "lint-staged": {
    "*.js": ["eslint --fix", "prettier --write"]
  }
}

Option C: Hybrid (pre-commit calls Husky)

repos:
  - repo: local
    hooks:
      - id: husky
        name: Husky hooks
        entry: npx husky run pre-commit
        language: system
        pass_filenames: false

Recommendation: Use pre-commit for multi-language projects, Husky for pure Node.js.

---

🔧 Troubleshooting

Hook Fails But You Want to Commit Anyway

# Skip hooks once
git commit --no-verify

# Skip specific hook
SKIP=flake8 git commit

# Skip multiple hooks
SKIP=flake8,mypy git commit

Warning: Use sparingly! Hooks exist for a reason.

Hook Takes Too Long

Option 1: Move to push stage

hooks:
  - id: mypy
    stages: [push]    # Only on push, not commit

Option 2: Limit files

hooks:
  - id: pytest
    files: ^tests/    # Only test files

Option 3: Use faster alternatives

# ❌ Slow
- repo: https://github.com/PyCQA/flake8

# ✅ Fast
- repo: https://github.com/astral-sh/ruff-pre-commit

Hook Doesn't Run

Debug checklist:

1. Check if installed:

   ls .git/hooks/pre-commit

2. Reinstall:

   pre-commit uninstall
   pre-commit install

3. Check file matching:

   pre-commit run --files path/to/file

4. Verbose output:

   pre-commit run --verbose --all-files

5. Clean cache:

   pre-commit clean
   pre-commit install-hooks

Hook Fails With Dependency Issues

Error: ModuleNotFoundError: No module named 'something'

Solution: Add additional_dependencies

hooks:
  - id: mypy
    additional_dependencies:
      - types-requests
      - types-pyyaml

Hook Modifies Files But Commit Still Fails

This is expected behavior!

1. Hook runs, modifies file
2. File is now different from what's staged
3. Commit fails with "Files were modified"
4. Stage the changes: git add .
5. Commit again

Auto-stage modified files (use carefully):

hooks:
  - id: black
    # Don't do this! It's confusing.
    # Better to manually review changes.

Hooks Work Locally But Fail in CI

Common causes:

1. Different hook versions:

   # Pin versions!
   rev: v4.5.0  # Not 'main' or 'master'

2. Different Python/Node versions:

   hooks:
     - id: black
       language_version: python3.11  # Specify version

3. Missing system dependencies:

   # GitHub Actions
   - name: Install system deps
     run: sudo apt-get install -y libxml2-dev

---

📚 Resources

Official Documentation

• Pre-commit Homepage: https://pre-commit.com/
• Configuration: https://pre-commit.com/#plugins
• Creating Hooks: https://pre-commit.com/#creating-new-hooks
• GitHub: https://github.com/pre-commit/pre-commit

Popular Hook Repositories

• Pre-commit Hooks: https://github.com/pre-commit/pre-commit-hooks
• Python: https://github.com/psf/black, https://github.com/astral-sh/ruff-pre-commit
• JavaScript: https://github.com/pre-commit/mirrors-eslint, https://github.com/pre-commit/mirrors-prettier
• Go: https://github.com/dnephin/pre-commit-golang
• Shell: https://github.com/shellcheck-py/shellcheck-py
• Docker: https://github.com/hadolint/hadolint

Hook Discovery

• Awesome Pre-commit: https://github.com/pre-commit/awesome-pre-commit-hooks
• Search Hooks: https://pre-commit.com/hooks.html

Learning Resources

• Official Tutorial: https://pre-commit.com/#quick-start
• Blog Posts: Search "pre-commit tutorial" on Dev.to, Medium
• Videos: YouTube "pre-commit hooks explained"

Community

• GitHub Discussions: https://github.com/pre-commit/pre-commit/discussions
• Stack Overflow: Tag pre-commit
• Discord/Slack: Various language communities

---

🎓 Learning Exercises

Exercise 1: Basic Setup (15 min)

Task: Set up pre-commit for a Python project.

Steps:

1. Install pre-commit: pip install pre-commit
2. Create .pre-commit-config.yaml with trailing-whitespace and end-of-file-fixer
3. Install hooks: pre-commit install
4. Create a test file with trailing spaces
5. Try to commit and verify hook catches it

Exercise 2: Multi-Language Project (30 min)

Task: Configure pre-commit for JavaScript + Python project.

Requirements:

• Python: Black formatter, flake8 linter
• JavaScript: Prettier formatter, ESLint
• Both: Trailing whitespace, YAML validation

Exercise 3: Custom Hook (45 min)

Task: Write a custom hook that prevents committing TODO comments.

Hint:

- repo: local
  hooks:
    - id: no-todos
      name: Block TODO comments
      entry: bash -c 'grep -r "TODO" src/ && exit 1 || exit 0'
      language: system
      pass_filenames: false

Exercise 4: Performance Optimization (30 min)

Task: You have slow hooks. Optimize the configuration.

Given:

hooks:
  - id: mypy        # Takes 30 seconds
  - id: pytest      # Takes 2 minutes
  - id: black       # Fast

Goal: Make commits fast while keeping quality checks.

Exercise 5: Team Rollout (60 min)

Task: Plan and execute pre-commit rollout for a 5-person team.

Deliverables:

• Configuration file
• Setup documentation
• CI integration
• Troubleshooting guide

---

🏆 Advanced Topics

Monorepo Strategies

Challenge: Different packages need different hooks.

Solution A: Multiple configs

monorepo/
├── .pre-commit-config.yaml      # Root - common hooks
├── packages/
│   ├── frontend/
│   │   └── .pre-commit-config.yaml    # JS hooks
│   └── backend/
│       └── .pre-commit-config.yaml    # Python hooks

Solution B: Conditional hooks

hooks:
  - id: black
    files: ^packages/backend/
    
  - id: prettier
    files: ^packages/frontend/

Performance Optimization

Techniques:

1. Parallel execution (automatic by default)
2. File filtering (reduce files checked)
3. Staged files only (default behavior)
4. Cache dependencies (automatic)

Measure performance:

time pre-commit run --all-files

Security-Focused Hooks

repos:
  # Secrets detection
  - repo: https://github.com/Yelp/detect-secrets
    rev: v1.4.0
    hooks:
      - id: detect-secrets
      
  # Security vulnerabilities
  - repo: https://github.com/PyCQA/bandit
    rev: 1.7.5
    hooks:
      - id: bandit
      
  # Dependency vulnerabilities
  - repo: https://github.com/Lucas-C/pre-commit-hooks-safety
    rev: v1.3.2
    hooks:
      - id: python-safety-dependencies-check

---

✅ Quick Reference

Common Commands

# Install
pip install pre-commit

# Setup hooks
pre-commit install                    # Install pre-commit hook
pre-commit install --hook-type pre-push  # Install pre-push hook
pre-commit install-hooks             # Install hook dependencies

# Run hooks
pre-commit run                       # Run on staged files
pre-commit run --all-files          # Run on all files
pre-commit run black                # Run specific hook
pre-commit run --files foo.py       # Run on specific files

# Maintenance
pre-commit autoupdate               # Update hook versions
pre-commit clean                    # Clean cache
pre-commit uninstall                # Remove hooks

# Skip hooks
git commit --no-verify              # Skip all hooks
SKIP=flake8 git commit             # Skip specific hook
SKIP=flake8,mypy git commit        # Skip multiple hooks

Minimal Configuration Template

repos:
  - repo: https://github.com/pre-commit/pre-commit-hooks
    rev: v4.5.0
    hooks:
      - id: trailing-whitespace
      - id: end-of-file-fixer
      - id: check-yaml
      - id: check-added-large-files

---

Happy pre-committing! 🚀

Last updated: 2025-11-30