Monorepo Performance

CI pipelines for monorepos need special optimization to avoid checking out the entire repo every time.

Strategy 1: Shallow clone — use fetch-depth: 1 in GitHub Actions. Fastest checkout, but no history.

Strategy 2: Path-based triggers — only run CI for directories that changed. Saves massive CI time in monorepos.

Strategy 3: Caching — persist the .git directory between CI runs. Incremental fetches instead of full clones.

Strategy 4: Sparse checkout in CI — only check out the directories being tested. Smaller working directory, faster operations.

Strategy 5: Monorepo tools (Nx, Turborepo, Lerna) — intelligent task scheduling based on dependency graphs. Only build and test affected packages.

# GitHub Actions optimized for monorepo
name: CI
on: [push, pull_request]

jobs:
  # Strategy 1: Shallow clone (fastest)
  fast-test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 1  # shallow clone

  # Strategy 2: Path-based triggers
  frontend-test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 2  # need 2 for diff
      - name: Check if frontend changed
        run: |
          if git diff --name-only HEAD~1 HEAD | grep -q "^packages/frontend/"; then
            echo "Frontend changed, running tests..."
            cd packages/frontend && npm test
          else
            echo "Frontend not changed, skipping."
          fi

  # Strategy 3: Sparse checkout in CI
  backend-test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          sparse-checkout: |
            packages/backend
            packages/shared
          sparse-checkout-cone-mode: true

  # Strategy 4: Cache .git between runs
  cached-checkout:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/cache@v3
        with:
          path: .git
          key: git-cache
      - run: git fetch  # incremental update instead of full clone