Replace implicit branch-based Pages publishing with an explicit deploy workflow

.github/workflows/deploy.yml

@@ -0,0 +1,75 @@
+name: deploy
+
+on:
+  pull_request:
+    paths:
+      - ".github/workflows/deploy.yml"
+      - "404.html"
+      - "Gemfile"
+      - "_config.yml"
+      - "_layouts/**"
+      - "_posts/**"
+      - "about.md"
+      - "index.html"
+  push:
+    branches:
+      - main
+    paths:
+      - ".github/workflows/deploy.yml"
+      - "404.html"
+      - "Gemfile"
+      - "_config.yml"
+      - "_layouts/**"
+      - "_posts/**"
+      - "about.md"
+      - "index.html"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: "3.2"
+          bundler-cache: true
+
+      - name: Configure Pages
+        uses: actions/configure-pages@v5
+
+      - name: Build site
+        env:
+          JEKYLL_ENV: production
+        run: bundle exec jekyll build
+
+      - name: Upload Pages artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: ./_site
+
+  deploy:
+    if: github.event_name != 'pull_request'
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4

.gitignore

@@ -1,5 +1,6 @@
 _site/
-Gemfile*
+vendor/bundle/
+.bundle/
 
 # Byte-compiled / optimized / DLL files
 __pycache__/

404.html

@@ -0,0 +1,25 @@
+---
+permalink: /404.html
+layout: default
+---
+
+<style type="text/css" media="screen">
+  .container {
+    margin: 10px auto;
+    max-width: 600px;
+    text-align: center;
+  }
+  h1 {
+    margin: 30px 0;
+    font-size: 4em;
+    line-height: 1;
+    letter-spacing: -1px;
+  }
+</style>
+
+<div class="container">
+  <h1>404</h1>
+
+  <p><strong>Page not found :(</strong></p>
+  <p>The requested page could not be found.</p>
+</div>

Gemfile

@@ -0,0 +1,20 @@
+source "https://rubygems.org"
+gem "github-pages", "~> 231", group: :jekyll_plugins
+
+group :jekyll_plugins do
+  gem "jekyll-feed", "~> 0.12"
+end
+
+# Windows and JRuby does not include zoneinfo files, so bundle the tzinfo-data gem
+# and associated library.
+platforms :mingw, :x64_mingw, :mswin, :jruby do
+  gem "tzinfo", ">= 1", "< 3"
+  gem "tzinfo-data"
+end
+
+# Performance-booster for watching directories on Windows
+gem "wdm", "~> 0.1.1", :platforms => [:mingw, :x64_mingw, :mswin]
+
+# Lock `http_parser.rb` gem to `v0.6.x` on JRuby builds since newer versions of the gem
+# do not have a Java counterpart.
+gem "http_parser.rb", "~> 0.6.0", :platforms => [:jruby]