writing-github-actions

# Writing GitHub Actions

Create GitHub Actions workflows for CI/CD pipelines, automated testing, deployments, and repository automation using YAML-based configuration with native GitHub integration.

## Purpose

GitHub Actions is the native CI/CD platform for GitHub repositories. This skill covers workflow syntax, triggers, job orchestration, reusable patterns, optimization techniques, and security practices specific to GitHub Actions.

**Core Focus:**
- Workflow YAML syntax and structure
- Reusable workflows and composite actions
- Matrix builds and parallel execution
- Caching and optimization strategies
- Secrets management and OIDC authentication
- Concurrency control and artifact management

**Not Covered:**
- CI/CD pipeline design strategy → See `building-ci-pipelines`
- GitOps deployment patterns → See `gitops-workflows`
- Infrastructure as code → See `infrastructure-as-code`
- Testing frameworks → See `testing-strategies`

## When to Use This Skill

Trigger this skill when:
- Creating CI/CD workflows for GitHub repositories
- Automating tests, builds, and deployments via GitHub Actions
- Setting up reusable workflows across multiple repositories
- Optimizing workflow performance with caching and parallelization
- Implementing security best practices for GitHub Actions
- Troubleshooting GitHub Actions YAML syntax or behavior

## Workflow Fundamentals

### Basic Workflow Structure

```yaml
name: CI
on:
  push:
    branches: [main]
  pull_request:
    branches: [main]

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v5
      - uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'
      - run: npm ci
      - run: npm test
```

**Key Components:**
- `name`: Workflow display name
- `on`: Trigger events (push, pull_request, schedule, workflow_dispatch)
- `jobs`: Job definitions (run in parallel by default)
- `runs-on`: Runner type (ubuntu-latest, windows-latest, macos-latest)
- `steps`: Seq