ci.yml: update to match main repo

.github/workflows/ci.yml

@@ -7,11 +7,27 @@ jobs:
   ci:
     runs-on: macos-latest
     steps:
-      - name: Check out Pull Request
+      - name: Update Homebrew
+        id: update_homebrew
         run: |
-          brew update-reset "$(brew --repository)"
+          set -euo pipefail
+
+          homebrew_repository="$(brew --repository)"
+
+          brew update-reset "${homebrew_repository}"
 
-          HOMEBREW_INSTALL_BUNDLER_GEMS_FIRST=1 brew config
+          echo "::set-output name=homebrew_gems_cache_id::$(shasum -a 256 "${homebrew_repository}/Library/Homebrew/Gemfile.lock" | cut -f1 -d ' ')"
+          echo "::set-output name=homebrew_gems_cache_dir::${homebrew_repository}/Library/Homebrew/vendor/bundle/ruby"
+      - name: Cache Homebrew Gems
+        uses: actions/cache@v2
+        with:
+          path: ${{ steps.update_homebrew.outputs.homebrew_gems_cache_dir }}
+          key: homebrew-gems-cache-${{ steps.update_homebrew.outputs.homebrew_gems_cache_id }}
+      - name: Install Homebrew Gems
+        run: brew install-bundler-gems
+      - name: Check out Pull Request
+        run: |
+          set -euo pipefail
 
           brew tap "${GITHUB_REPOSITORY}"