publish staging docs in Splice (#1045)

Signed-off-by: Itai Segall <itai.segall@digitalasset.com>

Author: isegall-da

.github/workflows/build.docs.yml

@@ -38,30 +38,11 @@ jobs:
           # as it finishes fastest and we want to ensure that it includes test sources.
           cmd: "Test/compile docs/bundle"
 
-      # TODO(#1028): Reenable this
-      # - name: Push documentation
-      #   uses: ./.github/actions/nix/run_bash_command_in_nix
-      #   if: github.ref == 'refs/heads/main' && github.event_name == 'push'
-      #   env:
-      #     GH_USER: ${{ github.actor }}
-      #     GH_TOKEN: ${{ secrets.GH_ISSUES }}
-      #   with:
-      #     additional_nix_args: "--keep GH_USER --keep GH_TOKEN"
-      #     cmd: |
-      #       REPO_DIR="$(mktemp -d)"
-      #       export GIT_SSH_COMMAND="/usr/bin/ssh"
-      #       git config --global user.email "splice-maintainers@digitalasset.com"
-      #       git config --global user.name "DA Automation"
-      #       git clone https://$GH_USER:$GH_TOKEN@github.com/digital-asset/decentralized-canton-sync.git "$REPO_DIR" -b docs
-      #       # Given that we just wanna overwrite anything an rm + cp seems more straightforward than an rsync.
-      #       rm -rf "$REPO_DIR/docs"
-      #       cp -r "docs/html/html" "$REPO_DIR/docs"
-      #       # Required to make GH service the _static directory properly.
-      #       touch "$REPO_DIR/docs/.nojekyll"
-      #       cd "$REPO_DIR"
-      #       git add .
-      #       git commit -m 'Update documentation'
-      #       git push origin docs
+      - name: Upload documentation artifacts
+        uses: actions/upload-pages-artifact@2d163be3ddce01512f3eea7ac5b7023b5d643ce1
+        if: github.ref == 'refs/heads/main' && github.event_name == 'push'
+        with:
+          path: docs/html/html
 
       - name: Post-SBT job
         uses: ./.github/actions/sbt/post_sbt

.github/workflows/post_merge.yml

@@ -20,3 +20,22 @@ jobs:
   ci:
     uses: ./.github/workflows/build.yml
     secrets: inherit
+
+  publish_docs:
+    if: github.ref == 'refs/heads/main'
+    needs: ci
+    runs-on: self-hosted-docker-tiny
+
+    permissions:
+      pages: write      # to deploy to Pages
+      id-token: write   # to verify the deployment originates from an appropriate source
+
+    # Deploy to the github-pages environment
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@854d7aa1b99e4509c4d1b53d69b7ba4eaf39215a