forgejo-ci: generate previews when in PR

.forgejo/workflows/preview.yaml

@@ -0,0 +1,47 @@
+on: 
+  pull_request:
+    types: [ assigned, opened, synchronize, reopened ]
+
+jobs:
+  render:
+    runs-on: x86_64
+    container:
+      image: alpine:latest
+    steps:
+      - name: Environment setup
+        run: |
+          apk add git ikiwiki po4a perl-yaml-tiny tree nodejs
+      - name: Repo pull
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+          token: ${{ secrets.PAGES_TOKEN }}
+      - name: Public repo pull
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          ref: public
+          path: public
+          token: ${{ secrets.PAGES_TOKEN }}
+      - name: Render website
+        run: |
+          rm -rf public/previews/$CURRENT_CONTENT_PATH || true
+          mkdir -p public/previews/${{ github.ref_name }}
+          sed -i "s|destdir.*|destdir: ./public/previews/${{ github.ref_name }}|" ikiwiki.setup
+          ikiwiki --setup ikiwiki.setup
+          cd public/previews
+          tree -d -H '.' -L 1 --noreport --charset utf-8 -T "Versions" -o index.html
+      - name: Website upload
+        run: |
+          rm -Rf public/.forgejo
+          mkdir -p public/.forgejo/workflows
+          cp .forgejo/workflows/deploy.yaml public/.forgejo/workflows/.
+          git log -1 --pretty=%B > commit.txt
+          cd public
+          date > previews/${{ github.ref_name}}/generated.txt
+          # Note: the following account information will not work on GHES
+          git config user.name "forgejo-actions[bot]"
+          git config user.email "dev@ayakael.net"
+          git add .
+          git commit -F ../commit.txt
+          git push