build: Add workflow for auto upgrading the makesystem.

.github/workflows/upgrade-makesystem.yml

@@ -0,0 +1,59 @@
+---
+name: Upgrade Makesystem
+
+on:
+  schedule:
+    - cron: '0 */3 * * *'
+  workflow_dispatch:
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  upgrade-makesystem:
+    name: Upgrade Makesystem
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Fetch full annotated tags metadata
+        run: git fetch --force --tags
+
+      - name: Set up makesystem
+        run: make makesystem_install
+
+      - name: Upgrade makesystem locally
+        run: make makesystem_upgrade
+
+      - name: Dump makesystem version
+        id: dump-makesystem-version
+        run: make github_dump_makesystem_version
+
+      - uses: tibdex/github-app-token@v1
+        id: generate-token
+        with:
+          app_id: ${{ secrets.UPGRADE_MAKESYSTEM_BOT_APP_ID }}
+          private_key: ${{ secrets.UPGRADE_MAKESYSTEM_BOT_APP_PRIVATE_KEY }}
+
+      - name: Create Pull Request
+        uses: peter-evans/create-pull-request@v3
+        with:
+          token: ${{ steps.generate-token.outputs.token }}
+          commit-message: |
+            build: [upgrade-makesystem-bot] Upgrade to v${{ steps.dump-makesystem-version.outputs.version }}.
+
+            Automated change generated by the Upgrade Makesystem Bot.
+          branch: upgrade-makesystem-bot/patch
+          delete-branch: true
+          title: |
+            Upgrade the makesystem to v${{ steps.dump-makesystem-version.outputs.version }}
+          body: |
+            Automated change generated by the Upgrade Makesystem Bot.