Git Hooks

Git Hooks

This skill provides guidance for implementing and maintaining Git hooks that enforce code quality standards before commits and pushes reach the repository.

When to use this skill

• Setting up Git hooks in a new repository
• Creating new pre-commit or pre-push hooks
• Debugging hook installation or execution issues
• Ensuring hooks follow team standards
• Migrating from manual hooks to version-controlled hooks
• Integrating with existing hook systems (Husky, pre-commit, lefthook)

Skill Contents

Sections

• When to use this skill
• Distributed Hooks (Informative Mode)
• Assets
• Architecture
• Instructions
• Hook Types
• Best Practices
• Hook Modes
• References
• Documentation
• Related Skills
• hk (ai-code-instructions only)
• Troubleshooting

Available Resources

📚 references/ - Detailed documentation

• go
• java
• python
• typescript

📦 assets/ - Templates and resources

• ensure node
• hooks bootstrap
• hooks bridge strategy
• hooks checks
• pre commit
• pre push

Distributed Hooks (Informative Mode)

For repositories receiving distributed AI rules, we provide informative hooks that:

• Never block commits or pushes (always exit 0)
• Warn about issues with clear fix commands
• Auto-detect Node.js via nvm, fnm, or system PATH (shows setup instructions if not found)
• Coexist with existing hook setups (Husky, pre-commit, lefthook)

How It Works

# Source location: global/skills/git-hooks/assets/
# Deployed to target repo as:

.git-hooks/
├── pre-commit          → Delegates to hooks-bootstrap.sh (same directory)
├── pre-push            → Delegates to hooks-bootstrap.sh (same directory)
├── ensure-node.sh      → Ensures Node.js 20+ is available
├── hooks-bootstrap.sh  → Entry point, loads Node, runs checks
└── hooks-checks.js     → Multi-language quality checks

Enabling Distributed Hooks

# Set Git to use our hooks directory
git config core.hooksPath .git-hooks

# Verify
git config --get core.hooksPath
# Should output: .git-hooks

Output Example

============================================================
  Bitso Quality Checks (Informative)
============================================================

  Pre-commit checks found some issues:

  [!] Linting: ESLint errors detected
      Run: mise run lint:fix

  [!] TypeScript: Type errors detected
      Run: npx tsc --noEmit

  These are recommendations. Your commit will proceed.
  For AI agents: Please address these issues before completing.

============================================================

Coexistence with Existing Hooks

See assets/hooks-bridge-strategy.md for detailed integration patterns with:

• Husky: Add our checks to .husky/pre-commit
• pre-commit (Python): Add as a local hook in .pre-commit-config.yaml
• lefthook: Add to lefthook.yml commands

Assets

Architecture

Recommended Directory Structure

project/
├── .git-hooks/              # Version-controlled hooks directory
│   ├── pre-commit           # Symlink → ../.scripts/pre-commit-hook.sh
│   └── pre-push             # Symlink → ../.scripts/pre-push-hook.sh
├── .scripts/
│   ├── setup-hooks.ts       # Hook installation script (runs on npm install)
│   ├── pre-commit-hook.sh   # Pre-commit hook implementation
│   ├── pre-push-hook.sh     # Pre-push hook implementation
│   └── lib/skills/          # Skill modules for hook operations
└── package.json             # Contains "prepare": "node .scripts/setup-hooks.ts"

Why This Architecture?

1. Version-controlled: Hooks live in .git-hooks/, tracked by Git
2. Automatic installation: npm install configures hooks via prepare script
3. Team consistency: Everyone gets the same hooks automatically
4. Implementation separation: Actual logic in .scripts/, symlinks in .git-hooks/
5. Skippable in CI: Setup script detects CI environment and skips

Instructions

Step 1: Create the Hooks Directory

mkdir -p .git-hooks

Step 2: Create the Setup Script

Create .scripts/setup-hooks.ts:

#!/usr/bin/env node
/**
 * Setup Git Hooks
 *
 * Runs on `npm install` via the "prepare" script.
 * Configures git to use .git-hooks/ for hooks.
 */

import fs from 'fs';
import path from 'path';
import { execSync } from 'child_process';
import { fileURLToPath } from 'url';

const __dirname = path.dirname(fileURLToPath(import.meta.url));

if (process.env.CI || process.env.SKIP_HOOKS) {
  console.log('⏭️  Skipping hook setup (CI or SKIP_HOOKS=true)');
  process.exit(0);
}

const ROOT_DIR = path.join(__dirname, '..');
const HOOKS_DIR = '.git-hooks';

function setupHooks() {
  if (!fs.existsSync(path.join(ROOT_DIR, '.git'))) {
    console.log('⚠️  Not a git repository, skipping hook setup');
    return;
  }

  const githooksPath = path.join(ROOT_DIR, HOOKS_DIR);
  if (!fs.existsSync(githooksPath)) {
    console.error(`❌ Hooks directory not found: ${HOOKS_DIR}`);
    process.exit(1);
  }

  // Set core.hooksPath
  try {
    execSync(`git config core.hooksPath ${HOOKS_DIR}`, { cwd: ROOT_DIR });
    console.log(`✅ Git hooks configured: core.hooksPath → ${HOOKS_DIR}`);
  } catch (error) {
    const err = error as Error;
    console.error('❌ Failed to set core.hooksPath:', err.message);
    process.exit(1);
  }
}

setupHooks();

Step 3: Configure package.json

Add the prepare script to automatically set up hooks on install:

{
  "scripts": {
    "prepare": "node .scripts/setup-hooks.ts"
  }
}

Step 4: Create Hook Implementation

Create hook scripts in .scripts/ following the template in the References section.

Step 5: Create Symlinks

Create symlinks in .git-hooks/ pointing to the implementation:

cd .git-hooks
ln -sf ../.scripts/pre-commit-hook.sh pre-commit
ln -sf ../.scripts/pre-push-hook.sh pre-push
chmod +x pre-commit pre-push

Step 6: Validate Hook Setup

# Run validation
npm run skills:hooks

# Or use CLI directly
node .scripts/skills-cli.ts git-hooks validate

Hook Types

Best Practices

1. Exit Codes Matter

# Exit 0 = success, commit/push proceeds
# Exit non-zero = failure, operation aborted
if ! npm test; then
  echo "Tests failed"
  exit 1
fi

2. Provide Clear Feedback

# Use colors and emojis for visibility
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
NC='\033[0m'

echo -e "${YELLOW}🔍 Running tests...${NC}"
if npm test --silent; then
  echo -e "${GREEN}   ✓ Tests passed${NC}"
else
  echo -e "${RED}   ✗ Tests failed${NC}"
  exit 1
fi

3. Keep Hooks Fast

Pre-commit hooks should complete in seconds, not minutes:

• Run only essential checks
• Use incremental/cached operations where possible
• Move heavy checks to pre-push

4. Allow Emergency Bypass

# Document how to skip in emergencies
git commit --no-verify  # Skip pre-commit
git push --no-verify    # Skip pre-push

5. Fail Early, Fail Fast

Order checks from fastest to slowest:

# 1. Fast checks first
echo "Checking for debug statements..."
if grep -r "console.log" src/; then
  echo "Remove debug statements before committing"
  exit 1
fi

# 2. Medium checks
echo "Running linter..."
npm run lint

# 3. Slow checks last
echo "Running tests..."
npm test

6. Handle Auto-Fixes

If a hook auto-fixes files, stage them:

if git diff --name-only | grep -q "formatted-file.js"; then
  git add formatted-file.js
  echo "Auto-formatted file added to commit"
fi

7. Never Add Coverage Exclusions as First Approach

IMPORTANT: When pre-push hooks fail due to coverage thresholds, the correct approach is:

1. Add tests to increase coverage (preferred)
2. Use --no-verify as a temporary emergency bypass if absolutely necessary
3. Never add exclusions to .c8rc.json, .nycrc, or coverage config

Why?

• Exclusions hide untested code and accumulate over time
• They defeat the purpose of coverage thresholds
• They make it harder to identify actual coverage gaps

Correct approach when coverage fails:

# 1. Run coverage report to identify gaps
npm run test:coverage:report

# 2. Add tests for uncovered lines
# ... write tests ...

# 3. Verify coverage now passes
npm run test:coverage

# 4. Commit and push normally
git push

Emergency bypass (use sparingly):

# Only when you MUST push immediately and will add tests in follow-up
git push --no-verify

# Document why in commit message or PR
# Create a ticket to add missing tests

Never do this:

// ❌ DON'T add exclusions to avoid writing tests
{
  "exclude": [
    ".scripts/new-module.ts"  // ❌ WRONG - write tests instead
  ]
}

Hook Modes

Git hooks support a unified mode system controlled via environment variables.

Mode Values

Environment Variables

Resolution Order

1. Hook-specific env var (e.g., BITSO_MISE_GIT_HOOKS_COMMIT)
2. Category env var (BITSO_MISE_GIT_HOOKS)
3. Global env var (BITSO_MISE_MODE)
4. Default: full

Example Configuration

In mise.local.toml:

[env]
# Run git hooks but don't fail locally
BITSO_MISE_GIT_HOOKS = "warn"

# Or: Fine-grained control
BITSO_MISE_GIT_HOOKS_COMMIT = "warn"  # Don't block commits
BITSO_MISE_GIT_HOOKS_PUSH = "full"    # But enforce on push

References

Technology-specific hook patterns are available in the references/ folder:

Documentation

For comprehensive documentation in the repository's docs/ directory, see:

• docs/ai-ide-management/concepts/git-hooks-architecture.md - System design and flow diagrams
• docs/ai-ide-management/how-tos/enable-git-hooks.md - Setup and troubleshooting
• docs/ai-ide-management/concepts/conflict-detection.md - How conflicts are detected during distribution

Related Skills

hk (ai-code-instructions only)

Note: This section is specific to the ai-code-instructions repository which uses hk as its git hook manager.

hk provides:

• Parallel execution: Runs multiple linters simultaneously
• Smart stashing: Safely stashes unstaged changes during hooks
• Progress reporting: Clear visual feedback during hook execution
• Profile-based configuration: Enable/disable checks via profiles

Configuration

hk is configured via hk.pkl in the repository root:

hooks {
  ["pre-commit"] {
    stash = "git"
    steps {
      ["eslint-staged"] = new Step { check = "node mise-tasks/check.ts eslint-staged" }
      ["tests-changed"] = new Step { check = "node mise-tasks/check.ts tests-changed" }
    }
  }
}

Common Commands

# Run hooks manually
hk run pre-commit     # Run pre-commit checks
hk run pre-push       # Run pre-push checks
hk run ci             # Run CI checks

# Check and fix
hk check              # Run all checks (read-only)
hk check --pr         # Check only files changed in current PR/branch
hk fix                # Auto-fix where possible
hk fix --pr           # Fix only files changed in current PR/branch

# Test step definitions
hk test               # Run step-defined tests

# Validate configuration
hk validate           # Validate hk.pkl

# Skip hooks
git commit --no-verify                    # Standard git bypass
HK_SKIP_HOOKS=pre-commit git commit       # Skip specific hook

Installation

# Install via Homebrew
brew install hk

# Download pkl packages (required for SSL cert compatibility)
pkl download-package --ca-certificates=/path/to/ca.pem \
  package://github.com/jdx/hk/releases/download/v1.36.0/hk@1.36.0

# Install hooks
hk install

Troubleshooting

Hooks not running

1. Verify hooks are installed:

   git config --get core.hooksPath
   # Should output: .git-hooks
   

2. Check symlinks are valid:

   ls -la .git-hooks/
   # Should show symlinks pointing to .scripts/*-hook.sh
   

3. Verify execute permissions:

   chmod +x .git-hooks/*
   chmod +x .scripts/*-hook.sh
   

Hooks running but failing

1. Run hooks manually to see full output:

   ./.scripts/pre-commit-hook.sh
   

2. Check for missing dependencies:

   npm install
   

3. Run with DEBUG mode:

   DEBUG=1 ./.scripts/pre-commit-hook.sh
   

Hooks too slow

1. Profile each check:

   time npm run lint
   time npm test
   

2. Move slow checks to pre-push

3. Use incremental/cached operations

4. Consider staged-files-only validation

Different behavior locally vs CI

1. CI should skip hooks (set CI=true)
2. CI runs validations directly, not via hooks
3. Ensure setup-hooks.ts checks for CI environment