Why This Matters

PR descriptions take 5–15 minutes each. An Action that auto-generates them saves developers time and ensures consistency. This project delivers a real CI integration.

Concept Explained

A GitHub Action that triggers on PR open. Calls Copilot API (or uses Copilot CLI) to generate a description from the diff. Posts as a comment or sets the description.

How It Works

Create .github/workflows/pr-description.yml. Use Copilot CLI or API to generate description from git diff. Update PR body or post as comment.

Step-by-Step Tutorial

1. Create workflow

2. Trigger on PR open

3. Get diff

4. Generate description

5. Post to PR

Real-World Example

A team added a PR-description generator Action. Saved 5–10 minutes per PR. Across 30 PRs/week: 3–5 hours saved. Reviewers loved consistent format.

Example Prompts / Commands / Code

# .github/workflows/pr-description.yml
name: Generate PR Description

on:
  pull_request:
    types: [opened]

jobs:
  generate-description:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Get diff
        id: diff
        run: echo "diff=$(git diff origin/main...HEAD)" >> $GITHUB_OUTPUT

      - name: Generate description
        id: desc
        run: |
          DESCRIPTION=$(echo "${{ steps.diff.outputs.diff }}" | \
            copilot 'Generate a PR description for this diff. \
                     Include: title, summary, test plan, risk notes. \
                     Format as markdown.' \
            --no-interactive)
          echo "description=$DESCRIPTION" >> $GITHUB_OUTPUT

      - name: Update PR
        uses: actions/github-script@v6
        with:
          script: |
            await github.rest.pulls.update({
              owner: context.repo.owner,
              repo: context.repo.repo,
              pull_number: context.payload.pull_request.number,
              body: `${{ steps.desc.outputs.description }}`
            });

Common Mistakes

• Generating without review — quality varies.
• Triggering on every PR edit — too noisy.
• Not using a template — descriptions inconsistent.
• Forgetting to redact secrets in diffs.

Best Practices

• Trigger on PR open only.
• Use a consistent template (title, summary, test plan, risk).
• Let author review and edit before finalizing.
• Redact secrets from diff before sending.
• Measure review time saved.

Troubleshooting

Practical Exercise

Professional Challenge

Frequently Asked Questions

Further Reading

• GitHub Actions docs

Official References

• GitHub Actions
• Copilot CLI

Related lessons: IN-46, IN-48