build: set up build workflow

Signed-off-by: Wouter Termont <[email protected]>

.github/workflows/auto-publish.yml

@@ -0,0 +1,75 @@
+
+##
+# This workflow renders a new version of each changed spec for GitHub Pages.
+##
+
+name: GitHub Pages workflow
+
+on:
+  push:
+    branches: [ main ]
+  workflow_dispatch: # for testing
+
+env:
+  build_dir: _gh_pages_build
+
+jobs:
+
+  conditional-build-deploy:
+    name: Build and deploy changed specs
+    runs-on: ubuntu-20.04
+    permissions:
+      contents: write
+    steps:
+
+      - name: Checkout branch
+        uses: actions/checkout@v4
+
+      - name: Detect changed specs
+        uses: dorny/paths-filter@v3
+        with:
+          base: ${{ github.ref }}
+          filters: |
+            level0: level0/**
+          # level1: level1/** 
+          # level2: level2/**
+        id: filter
+
+      - name: Set Python version
+        uses: actions/setup-python@v5
+        with:
+          python-version: '>=3.9'
+
+      - name: Install Bikeshed
+        run: pipx install --python $(which python) --quiet bikeshed
+
+      - name: Setup build environment
+        run: |
+          mkdir -p "${{ env.build_dir }}"
+          cp common/* level0/
+          echo "time=$(date +"%Y%m%d%H%M%S")" >> "$GITHUB_OUTPUT"
+        # && cp common/* level1/ && cp common/* level2/
+
+      - name: Build Level 0
+        if: steps.filter.outputs.level0 == 'true'
+        run: bikeshed spec level0/index.bs "${{ env.build_dir }}/level0/index.html"
+        id: bikeshed
+
+      # - name: Build Level 1
+      #   if: steps.filter.outputs.level1 == 'true'
+      #   run: bikeshed spec level1/index.bs "${{ env.build_dir }}/level1/index.html"
+      #   id: bikeshed
+
+      # - name: Build Level 2
+      #   if: steps.filter.outputs.level2 == 'true'
+      #   run: bikeshed spec level2/index.bs "${{ env.build_dir }}/level2/index.html"
+      #   id: bikeshed
+
+      - name: Deploy to GitHub Pages
+        uses: JamesIves/github-pages-deploy-action@v4
+        with:
+          folder: "${{ env.build_dir }}"
+          target-folder: "specs"
+          commit-message: "publish: changes at ${{ steps.bikeshed.outputs.time }}"
+          branch: gh-pages
+          tag: "v${{ steps.bikeshed.outputs.time }}"