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tessl/go-lefthook

A Git hooks manager for Node.js, Ruby, Python and many other types of projects, written in Go for speed and cross-platform compatibility.

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Overview
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hook-execution.mddocs/

Hook Execution

Lefthook's hook execution engine provides powerful capabilities for running Git hooks with parallel execution, file filtering, and comprehensive error handling.

Execution Modes

Parallel Execution

Execute multiple commands concurrently to improve performance:

pre-commit:
  parallel: true  # Enable parallel execution
  commands:
    lint:
      run: eslint {staged_files}
    test:
      run: npm test
    format:
      run: prettier --write {staged_files}

Sequential Execution

Execute commands one after another (default behavior):

pre-commit:
  parallel: false  # Sequential execution (default)
  commands:
    build:
      run: npm run build
    test:
      run: npm test  # Runs after build completes

Piped Execution

Chain command outputs together:

pre-commit:
  piped: true  # Enable piped execution
  commands:
    generate:
      run: generate-data
    process:
      run: process-data  # Receives output from generate-data

File Processing

Staged Files Processing

Process only Git staged files (default for pre-commit):

pre-commit:
  commands:
    lint:
      glob: "*.js"
      run: eslint {staged_files}  # Only staged JS files

All Files Processing

Process all repository files:

# Via command line
lefthook run pre-commit --all-files

# Via configuration
pre-commit:
  commands:
    full-lint:
      run: eslint {all_files}

Custom File Selection

Use Git commands to select specific files:

pre-push:
  commands:
    test-changed:
      files: git diff --name-only HEAD @{push}
      glob: "*.js"
      run: jest {files}

File Filtering

Glob Pattern Matching

# Single file type
glob: "*.js"

# Multiple file types  
glob: "*.{js,ts,jsx,tsx}"

# Directory-specific
glob: "src/**/*.js"

# Complex patterns
glob: "{src,test}/**/*.{js,ts}"

Exclusion Patterns

commands:
  lint:
    glob: "*.js"
    exclude: "(test|spec)\.js$"  # Regex pattern to exclude test files
    run: eslint {files}

File Template Variables

# Available file templates
{files}        # Files matched by glob after filtering
{staged_files} # All staged files (unfiltered)
{push_files}   # Files being pushed
{all_files}    # All repository files

Execution Control

Priority-based Execution

Control execution order with priority values:

pre-commit:
  commands:
    format:
      priority: 1      # Runs first
      run: prettier --write {staged_files}
      stage_fixed: true
      
    lint:
      priority: 2      # Runs second  
      run: eslint {staged_files}
      
    test:
      priority: 3      # Runs last
      run: npm test

Conditional Execution

Git State Conditions

# Skip during merge conflicts
skip: merge

# Skip during rebase
skip: rebase

# Only run during merge
only: merge

# Multiple conditions
skip: [merge, rebase]
only: [merge, rebase]

Tag-based Filtering

pre-commit:
  exclude_tags: [slow]  # Exclude commands tagged as 'slow'
  
  commands:
    quick-lint:
      tags: [fast, required]
      run: quick-linter
      
    slow-test:
      tags: [slow]
      run: comprehensive-test-suite

Interactive Execution

Interactive Commands

Allow commands to interact with user input:

pre-push:
  commands:
    confirm-deploy:
      interactive: true
      run: ./scripts/confirm-deployment.sh

Standard Input Handling

Provide stdin to commands:

commit-msg:
  commands:
    validate-message:
      use_stdin: true
      run: ./scripts/validate-commit-msg.sh

Error Handling and Recovery

Stage Fixed Files

Automatically stage files modified by commands:

pre-commit:
  commands:
    format:
      run: prettier --write {staged_files}
      stage_fixed: true  # Stage files after formatting
      
    lint:
      run: eslint --fix {staged_files}  
      stage_fixed: true  # Stage files after linting

Custom Failure Messages

Provide helpful error messages:

pre-commit:
  commands:
    dependencies:
      run: npm ci
      fail_text: "Dependencies failed to install. Run 'npm install' to fix."
      
    test:
      run: npm test
      fail_text: "Tests failed. Fix failing tests before committing."

Execution Strategies

pre-commit:
  follow: true  # Continue execution even if commands fail
  
  commands:
    lint:
      run: eslint {staged_files}
    test:
      run: npm test    # Runs even if lint fails when follow: true

Environment and Context

Environment Variables

pre-commit:
  commands:
    test:
      env:
        NODE_ENV: test
        CI: true
        DATABASE_URL: test-db-url
      run: npm test

Working Directory

pre-commit:
  commands:
    frontend-lint:
      root: ./frontend  # Change to frontend directory
      run: npm run lint
      
    backend-test:
      root: ./backend   # Change to backend directory  
      run: go test ./...

Script Execution

Script Runners

Execute custom scripts with specific interpreters:

pre-commit:
  scripts:
    bash-script:
      runner: bash
      # Executes ./lefthook/pre-commit/bash-script
      
    node-script:
      runner: node
      env:
        NODE_ENV: development
      # Executes ./lefthook/pre-commit/node-script
      
    python-script:
      runner: python
      # Executes ./lefthook/pre-commit/python-script

Script Directory Structure

.lefthook/
├── pre-commit/
│   ├── bash-script          # Bash script
│   ├── node-script.js       # Node.js script  
│   └── python-script.py     # Python script
├── pre-push/
│   └── deployment-check.sh
└── commit-msg/
    └── validate-format.rb

Performance Optimization

Parallel Processing

pre-commit:
  parallel: true  # Enable parallel execution
  commands:
    # These run concurrently
    lint: { run: "eslint {staged_files}" }
    test: { run: "npm test" }
    format: { run: "prettier --write {staged_files}" }

File Filtering Optimization

pre-commit:
  commands:
    # Only process relevant files
    js-lint:
      glob: "*.{js,ts}"          # Pre-filter files
      run: eslint {staged_files}
      
    # Use exclude for better performance
    all-lint:
      glob: "*"
      exclude: "node_modules|dist|build"  # Exclude large directories
      run: generic-linter {files}

Debugging and Monitoring

Verbose Output

# Enable verbose logging
lefthook run pre-commit --verbose

# Show execution details, timing, and file processing

Execution Summary

Lefthook provides execution summaries showing:

  • Commands executed
  • Execution time
  • Files processed
  • Success/failure status
  • Skip reasons

Log Output Control

# Control output verbosity
output:
  - meta     # Show metadata (default)
  - success  # Show success messages
  - failure  # Show failure messages (default)
  - summary  # Show execution summary (default)
  - skips    # Show skipped commands

docs

cli-commands.md

configuration.md

hook-execution.md

index.md

tile.json