pkg installer: install cached API data.

Continuing with the goals of making the installer:
- more useful
- entirely offline

Let's pre-download the API data from a `brew update` run and install it
into the logged-in user's home directory.

.github/workflows/build-pkg.yml

@@ -20,17 +20,24 @@ jobs:
       TEMPORARY_KEYCHAIN_FILE: 'homebrew_installer_signing.keychain-db'
       MIN_MACOS_VERSION: '11.0'
       PKG_APPLE_DEVELOPER_TEAM_ID: ${{ secrets.PKG_APPLE_DEVELOPER_TEAM_ID }}
+      HOMEBREW_NO_ANALYTICS_THIS_RUN: 1
+      HOMEBREW_NO_ANALYTICS_MESSAGE_OUTPUT: 1
     steps:
-      - name: Checkout to brew subdirectory
+      - name: Checkout Homebrew to brew subdirectory
         uses: actions/checkout@v3
         with:
           path: brew
           fetch-depth: 0
           persist-credentials: false
 
+      - name: Update Homebrew
+        env:
+          HOMEBREW_CACHE: "${GITHUB_WORKSPACE}/brew/cache"
+        run: brew/bin/brew update --auto-update
+
       - name: Get Homebrew version from Git
         id: print-version
-        run: echo "version=$(git -C brew describe --tags --always)" >> "${GITHUB_OUTPUT}"
+        run: echo "version=$(git -C brew/bin/brew describe --tags --always)" >> "${GITHUB_OUTPUT}"
 
       - name: Install Pandoc
         run: brew install pandoc

package/scripts/postinstall

@@ -50,3 +50,9 @@ then
 else
   chown -R "${logged_in_user}:${group}" .
 fi
+
+# move API cache to ~/Library/Caches/Homebrew
+user_api_cache_dir=~"${logged_in_user}"/Library/Caches/Homebrew/api
+mkdir -p "${user_api_cache_dir}"
+mv "${homebrew_directory}/cache/api/"* "${user_api_cache_dir}"
+rm -rf "${homebrew_directory}/cache"