workflows/tests: split out jobs.

Separate out the slow parts of tests into jobs that can be run in
parallel.

Also:
- general refactoring from YAML linter.
- don't build on `macOS-latest` now that Big Sur is the latest stable
  release.
- Use `runner.os` when it improves readability over `matrix.os`.

.github/workflows/tests.yml

@@ -1,25 +1,128 @@
-name: GitHub Actions CI
+name: CI
 on:
   push:
-    branches: master
+    branches:
+      - master
   pull_request:
 env:
   HOMEBREW_DEVELOPER: 1
   HOMEBREW_NO_AUTO_UPDATE: 1
 jobs:
-  tests:
+  syntax:
     if: github.repository == 'Homebrew/brew'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set up Homebrew
+        id: set-up-homebrew
+        uses: Homebrew/actions/setup-homebrew@master
+
+      - name: Cache Bundler RubyGems
+        uses: actions/cache@v1
+        with:
+          path: ${{ steps.set-up-homebrew.outputs.gems-path }}
+          key: ${{ runner.os }}-rubygems-${{ steps.set-up-homebrew.outputs.gems-hash }}
+          restore-keys: ${{ runner.os }}-rubygems-
+
+      - run: brew install-bundler-gems
+
+      - run: brew style --display-cop-names
+
+      - run: brew man --fail-if-changed
+
+      - run: brew typecheck
+
+      - name: Run vale for docs linting
+        run: |
+          brew install vale
+          vale docs/
+
+      - name: Lint Dockerfile
+        run: |
+          brew install hadolint
+          hadolint Dockerfile
+
+  brew-tests:
+    needs: syntax
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        include:
+          - test-flags: --no-compat --online
+          - test-flags: --generic --online
+          - test-flags: --online
+    steps:
+      - name: Set up Homebrew
+        id: set-up-homebrew
+        uses: Homebrew/actions/setup-homebrew@master
+
+      - name: Cache Bundler RubyGems
+        uses: actions/cache@v1
+        with:
+          path: ${{ steps.set-up-homebrew.outputs.gems-path }}
+          key: ${{ runner.os }}-rubygems-${{ steps.set-up-homebrew.outputs.gems-hash }}
+          restore-keys: ${{ runner.os }}-rubygems-
+
+      - run: brew install-bundler-gems
+
+      - name: Run brew tests
+        run: |
+          # brew tests doesn't like world writable directories
+          sudo chmod -R g-w,o-w /home/linuxbrew/.linuxbrew/Homebrew
+
+          brew tests ${{ matrix.test_flags }}
+        env:
+          HOMEBREW_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  brew-tests-coverage:
+    needs: syntax
+    runs-on: macos-11.0
+    steps:
+      - name: Set up Homebrew
+        id: set-up-homebrew
+        uses: Homebrew/actions/setup-homebrew@master
+
+      - name: Set up Xcode
+        run: sudo xcode-select --switch /Applications/Xcode_12.2.app/Contents/Developer
+
+      - name: Install brew tests dependencies
+        run: |
+          brew install subversion
+          Library/Homebrew/shims/scm/svn --homebrew=print-path
+          which svn
+          which svnadmin
+
+      - name: Cache Bundler RubyGems
+        uses: actions/cache@v1
+        with:
+          path: ${{ steps.set-up-homebrew.outputs.gems-path }}
+          key: ${{ runner.os }}-rubygems-${{ steps.set-up-homebrew.outputs.gems-hash }}
+          restore-keys: ${{ runner.os }}-rubygems-
+
+      - run: brew install-bundler-gems
+
+      - run: brew tests --online --coverage
+        env:
+          HOMEBREW_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+          # set variables for coverage reporting
+          HOMEBREW_CODECOV_TOKEN: 3ea0364c-80ce-47a3-9fba-93a940d4b5d7
+
+          # These cannot be queried at the macOS level on GitHub Actions.
+          HOMEBREW_LANGUAGES: en-GB
+
+  more-tests-and-syntax:
+    needs: syntax
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest, macOS-latest, macOS-11.0]
+        os:
+          - ubuntu-latest
+          - macos-11.0
         include:
           - os: ubuntu-latest
-            core-tap: 'linuxbrew-core'
+            core-tap: "linuxbrew-core"
-          - os: macOS-latest
+          - os: macos-11.0
-            core-tap: 'homebrew-core'
+            core-tap: "homebrew-core"
-          - os: macOS-11.0
-            core-tap: 'homebrew-core'
     steps:
       - name: Set up Homebrew
         id: set-up-homebrew
@@ -33,7 +136,7 @@ jobs:
       - run: brew test-bot --only-cleanup-before
 
       - name: Set up Xcode
-      if: matrix.os == 'macOS-11.0'
+        if: matrix.os == 'macos-11.0'
         run: sudo xcode-select --switch /Applications/Xcode_12.2.app/Contents/Developer
 
       - run: brew config
@@ -48,64 +151,23 @@ jobs:
 
       - run: brew doctor
 
-    - name: Set up Homebrew official command taps
-      run: |
-        # Setup taps needed for 'brew tests' and 'brew man'
-        cd "$(brew --repo)"
-
-        if [ "$RUNNER_OS" = "macOS" ]; then
-          brew update-reset Library/Taps/homebrew/homebrew-bundle \
-                            Library/Taps/homebrew/homebrew-cask \
-                            Library/Taps/homebrew/homebrew-cask-versions \
-                            Library/Taps/homebrew/homebrew-services
-        else
-          brew update-reset Library/Taps/homebrew/homebrew-services
-        fi
-
-    - name: Run brew style on Homebrew/brew
-      run: brew style --display-cop-names
-
-    - name: Run brew man
-      run: brew man --fail-if-changed
-
-    - name: Install brew tests dependencies
-      if: matrix.os != 'ubuntu-latest'
-      run: |
-        brew install subversion
-        Library/Homebrew/shims/scm/svn --homebrew=print-path
-        which svn
-        which svnadmin
-
-    - name: Run brew tests
-      run: |
-        # brew tests doesn't like world writable directories
-        if [[ "$RUNNER_OS" = "Linux" ]]; then
-            sudo chmod -R g-w,o-w /home/linuxbrew/.linuxbrew/Homebrew
-        fi
-
-        # don't bother running all tests on both platforms (for speed)
-        if [ "$RUNNER_OS" = "Linux" ]; then
-          brew tests --no-compat --online
-          brew tests --generic --online
-          brew tests --online
-        else
-          brew tests --online --coverage
-        fi
-      env:
-        HOMEBREW_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
-        # set variables for coverage reporting
-        HOMEBREW_CODECOV_TOKEN: 3ea0364c-80ce-47a3-9fba-93a940d4b5d7
-
-        # These cannot be queried at the macOS level on GitHub Actions.
-        HOMEBREW_LANGUAGES: en-GB
-
       - name: Run brew update-tests
+        if: github.event_name == 'pull_request'
         run: |
           brew update-test
           brew update-test --to-tag
           brew update-test --commit=HEAD
-      if: github.event_name == 'pull_request'
+
+      - name: Set up all Homebrew taps
+        if: runner.os == 'macOS'
+        run: |
+          brew update-reset Library/Taps/homebrew/homebrew-bundle \
+                            Library/Taps/homebrew/homebrew-cask \
+                            Library/Taps/homebrew/homebrew-services
+          brew tap homebrew/cask
+          brew tap homebrew/cask-drivers
+          brew tap homebrew/cask-fonts
+          brew tap homebrew/cask-versions
 
       - name: Run brew readall on all taps
         run: brew readall --aliases
@@ -114,18 +176,16 @@ jobs:
         run: brew style --display-cop-names homebrew/core
 
       - name: Run brew style on official taps
-      run: brew style --display-cop-names homebrew/bundle homebrew/services homebrew/test-bot
+        if: runner.os == 'macOS'
+        run: |
+          brew style --display-cop-names homebrew/bundle \
+                                         homebrew/services \
+                                         homebrew/test-bot
 
       - name: Run brew style on cask taps
-      if: matrix.os != 'ubuntu-latest'
+        if: runner.os == 'macOS'
         run: |
-        brew tap homebrew/cask
+          brew style --display-cop-names homebrew/cask \
-        brew tap homebrew/cask-drivers
-        brew tap homebrew/cask-fonts
-        brew tap homebrew/cask-versions
-
-        brew style --display-cop-names \
-          homebrew/cask \
                                          homebrew/cask-drivers \
                                          homebrew/cask-fonts \
                                          homebrew/cask-versions
@@ -133,37 +193,46 @@ jobs:
       - name: Run brew audit --skip-style on all taps
         run: brew audit --skip-style
 
-    - run: brew typecheck
+  docker:
-
+    needs: syntax
-    - name: Run vale for docs linting
+    runs-on: ubuntu-latest
-      run: |
+    steps:
-        brew install vale
+      - name: Set up Homebrew
-        vale docs/
+        id: set-up-homebrew
-
+        uses: Homebrew/actions/setup-homebrew@master
-    - name: Lint Dockerfile
-      if: matrix.os == 'ubuntu-latest'
-      run: |
-        brew install hadolint
-        hadolint Dockerfile
 
       - name: Build Docker image
-      if: matrix.os == 'ubuntu-latest'
         run: docker build -t brew --build-arg=version=16.04 .
 
-    - name: Run brew test-bot --only-formulae --test-default-formula
-      run: |
-        if [ "$RUNNER_OS" = "Linux" ]; then
-          docker run --rm brew brew test-bot --only-formulae --test-default-formula
-        else
-          brew test-bot --only-formulae --test-default-formula
-        fi
-
       - name: Deploy the Docker image to GitHub Packages and Docker Hub
-      if: matrix.os == 'ubuntu-latest' && github.ref == 'refs/heads/master'
+        if: github.ref == 'refs/heads/master'
         run: |
-        echo ${{secrets.HOMEBREW_GITHUB_PACKAGES_API_TOKEN}} | docker login ghcr.io -u BrewTestBot --password-stdin
+          echo ${{secrets.HOMEBREW_GITHUB_PACKAGES_API_TOKEN}} | \
+            docker login ghcr.io -u BrewTestBot --password-stdin
           docker tag brew "ghcr.io/homebrew/ubuntu16.04:master"
           docker push "ghcr.io/homebrew/ubuntu16.04:master"
-        echo ${{secrets.DOCKER_TOKEN}} | docker login -u brewtestbot --password-stdin
+          echo ${{secrets.DOCKER_TOKEN}} | \
+            docker login -u brewtestbot --password-stdin
           docker tag brew "homebrew/ubuntu16.04:master"
           docker push "homebrew/ubuntu16.04:master"
+
+  test-bot-default-formula:
+    needs: syntax
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os:
+          - ubuntu-latest
+          - macos-11.0
+    steps:
+      - name: Set up Homebrew
+        id: set-up-homebrew
+        uses: Homebrew/actions/setup-homebrew@master
+
+      - name: Set up Xcode
+        if: matrix.os == 'macos-11.0'
+        run: sudo xcode-select --switch /Applications/Xcode_12.2.app/Contents/Developer
+
+      - run: brew test-bot --only-cleanup-before
+
+      - run: brew test-bot --only-formulae --test-default-formula