add gh pages workflow

.github/workflows/deploy-gh-pages.yaml

@@ -0,0 +1,43 @@
+name: "Build and Deploy to GitHub Pages"
+# Based on https://docs.github.com/en/pages/getting-started-with-github-pages/using-custom-workflows-with-github-pages
+
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.3'
+      - name: Install dependencies
+        run: |
+          gem install -g dependencies/Gemfile
+      - run: |
+          mkdir _site
+          cp -r spec _site/spec
+          make -C _site/spec
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: _site/
+
+  deploy:
+    if: github.ref == 'refs/heads/main'
+    permissions:
+      contents: read
+      pages: write
+      id-token: write
+    runs-on: ubuntu-latest
+    needs: build
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4

dependencies/Gemfile

@@ -0,0 +1,2 @@
+source 'https://rubygems.org'
+gem 'asciidoctor'

dependencies/README

@@ -0,0 +1,3 @@
+Dependency files for build processes
+
+Used by workflows in .github/workflows

spec/Makefile

@@ -1,6 +1,8 @@
 
+TARGETS = d16n-v1_0.html latest.html
+
 .PHONY: all
-all: d16n-v1_0.html
+all: $(TARGETS)
 
 .PHONY: preview
 preview: d16n-v1_0.html
@@ -9,3 +11,11 @@ preview: d16n-v1_0.html
 
 d16n-v1_0.html: d16n-v1_0.adoc
 	asciidoctor $<
+
+latest.html: d16n-v1_0.html
+	cp $< $@
+
+
+.PHONY: clean
+clean:
+	$(RM) $(TARGETS)

spec/README.md

@@ -0,0 +1,14 @@
+## Tools
+
+### `asciidoctor`
+
+You may find it useful to [install][adoc-install] `asciidoctor` to build locally.
+
+[adoc-install]: https://docs.asciidoctor.org/asciidoctor/latest/install/
+
+Unless the world has changed, it's likely a case of
+- `brew install asciidoctor` on macOS
+- `sudo apt-get install asciidoctor` on Ubuntu or
+- `nix-shell -p asciidoctor` on NixOS
+
+There's probably also a preview extension for your editor.