workflows/tests: consolidate macOS tests.

We have a limited number of macOS workers (for the Homebrew
organisation) and queuing these seems to be slowing things down overall
compared to when we had one big job.

Linux throughput is still significantly quicker so it makes sense to
split up those jobs for providing quick feedback on breakages that are
cross-platform (which ends up being most but definitely not all of
them).

.github/workflows/tests.yml

@@ -43,17 +43,8 @@ jobs:
           hadolint Dockerfile
 
   tap-syntax:
-    name: ${{ matrix.name }}
+    name: tap syntax (Linux)
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        include:
-          - name: tap syntax (Linux)
-            os: ubuntu-latest
-            core-tap: linuxbrew-core
-          - name: tap syntax (macOS)
-            os: macos-latest
-            core-tap: homebrew-core
     steps:
       - name: Set up Homebrew
         id: set-up-homebrew
@@ -61,10 +52,6 @@ jobs:
 
       - run: brew test-bot --only-cleanup-before
 
-      - name: Set up Xcode
-        if: matrix.os == 'macos-11.0'
-        run: sudo xcode-select --switch /Applications/Xcode_12.2.app/Contents/Developer
-
       - run: brew config
 
       - name: Cache Bundler RubyGems
@@ -86,63 +73,23 @@ jobs:
           brew update-test --to-tag
           brew update-test --commit=HEAD
 
-      - name: Set up all Homebrew taps
-        if: runner.os == 'macOS'
-        run: |
-          brew tap homebrew/cask
-          brew tap homebrew/cask-drivers
-          brew tap homebrew/cask-fonts
-          brew tap homebrew/cask-versions
-          brew update-reset Library/Taps/homebrew/homebrew-bundle \
-                            Library/Taps/homebrew/homebrew-cask \
-                            Library/Taps/homebrew/homebrew-cask-versions \
-                            Library/Taps/homebrew/homebrew-services
-
       - name: Run brew readall on all taps
         run: brew readall --aliases
 
-      - name: Run brew style on ${{ matrix.core-tap }}
+      - name: Run brew style on linuxbrew-core
         run: brew style --display-cop-names homebrew/core
 
-      - name: Run brew style on official taps
-        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: runner.os == 'macOS'
-        run: |
-          brew style --display-cop-names homebrew/cask \
-                                         homebrew/cask-drivers \
-                                         homebrew/cask-fonts \
-                                         homebrew/cask-versions
-
       - name: Run brew audit --skip-style on all taps
         run: brew audit --skip-style
 
   vendored-gems:
-    name: ${{ matrix.name }}
+    name: vendored gems (Linux)
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        include:
-          - name: vendored gems (Linux)
-            os: ubuntu-latest
-            core-tap: linuxbrew-core
-          - name: vendored gems (macOS)
-            os: macos-11.0
-            core-tap: homebrew-core
     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
-
       - name: Configure Git user
         uses: Homebrew/actions/git-user-config@master
         with:
@@ -180,39 +127,21 @@ jobs:
 
   tests:
     name: ${{ matrix.name }}
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         include:
           - name: tests (no-compatibility mode)
-            os: ubuntu-latest
             test-flags: --no-compat --online --coverage
           - name: tests (generic OS)
-            os: ubuntu-latest
             test-flags: --generic --online --coverage
           - name: tests (Linux)
-            os: ubuntu-latest
-            test-flags: --online --coverage
-          - name: tests (macOS)
-            os: macos-11.0
             test-flags: --online --coverage
     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
-
-      - name: Install brew tests dependencies
-        if: runner.os == 'macOS'
-        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:
@@ -225,42 +154,105 @@ jobs:
 
       - name: Run brew tests
         run: |
-          if ${{ runner.os == 'Linux' }}; then
+          # brew tests doesn't like world writable directories
-            # brew tests doesn't like world writable directories
+          sudo chmod -R g-w,o-w /home/linuxbrew/.linuxbrew/Homebrew
-            sudo chmod -R g-w,o-w /home/linuxbrew/.linuxbrew/Homebrew
-          elif ${{ runner.os == 'macOS' }}; then
-            # These cannot be queried at the macOS level on GitHub Actions.
-            export HOMEBREW_LANGUAGES='en-GB'
-          fi
-
-          if ${{ contains(matrix.test-flags, '--coverage') }}; then
-            # Set variables for coverage reporting.
-            export HOMEBREW_CODECOV_TOKEN='3ea0364c-80ce-47a3-9fba-93a940d4b5d7'
-          fi
 
           brew tests ${{ matrix.test-flags }}
         env:
           HOMEBREW_GITHUB_API_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          HOMEBREW_CODECOV_TOKEN: 3ea0364c-80ce-47a3-9fba-93a940d4b5d7
 
-  test-default-formula:
+  test-default-formula-linux:
-    name: ${{ matrix.name }}
+    name: test default formula (Linux)
-    runs-on: ${{ matrix.os }}
+    runs-on: ubuntu-latest
-    strategy:
+    steps:
-      matrix:
+      - name: Set up Homebrew
-        include:
+        id: set-up-homebrew
-          - name: test default formula (Linux)
+        uses: Homebrew/actions/setup-homebrew@master
-            os: ubuntu-latest
+
-          - name: test default formula (macOS)
+      - run: brew test-bot --only-cleanup-before
-            os: macos-latest
+
+      - run: brew test-bot --only-formulae --test-default-formula
+
+  test-everything:
+    name: test everything (macOS)
+    runs-on: 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 config
+
+      # Can't cache this because we need to check that it doesn't fail the
+      # "uncommitted RubyGems" step with a cold cache.
+      - name: Install Bundler RubyGems
+        run: brew install-bundler-gems
+
+      - name: Check for uncommitted RubyGems
+        run: git diff --stat --exit-code Library/Homebrew/vendor/bundle/ruby
+
+      - run: brew doctor
+
+      - 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
+
+      - name: Set up all Homebrew taps
+        run: |
+          brew tap homebrew/cask
+          brew tap homebrew/cask-drivers
+          brew tap homebrew/cask-fonts
+          brew tap homebrew/cask-versions
+          brew update-reset Library/Taps/homebrew/homebrew-bundle \
+                            Library/Taps/homebrew/homebrew-cask \
+                            Library/Taps/homebrew/homebrew-cask-versions \
+                            Library/Taps/homebrew/homebrew-services
+
+      - name: Run brew readall on all taps
+        run: brew readall --aliases
+
+      - name: Run brew style on homebrew-core
+        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
+
+      - name: Run brew style on cask taps
+        run: |
+          brew style --display-cop-names homebrew/cask \
+                                         homebrew/cask-drivers \
+                                         homebrew/cask-fonts \
+                                         homebrew/cask-versions
+
+      - name: Run brew audit --skip-style on all taps
+        run: brew audit --skip-style
+
+      - name: Install brew tests dependencies
+        run: |
+          brew install subversion
+          Library/Homebrew/shims/scm/svn --homebrew=print-path
+          which svn
+          which svnadmin
+
+      - name: Run brew tests
+        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
+
       - run: brew test-bot --only-formulae --test-default-formula