[ci] Hopefully cured bitrot now

The issue turned out to be to do with modifying external actions: it is
only possible to specify `defaults.run.working-directory` for jobs, but
**not** for actions which are pulled in with `using`.

I've fixed this (temporarily?) by just copying the jobs from the Pelican
CI. Hopefully opening a PR against that should allow us to just use
their CI action.

Author: CodingCellist

.github/workflows/pelican.yml

@@ -2,7 +2,7 @@
 ## Pages.
 ## The contents of this file were based on the existing deployment templates in
 ## https://github.com/actions/starter-workflows/tree/main/pages
-## as well as the official Pelican docs at
+## as well as the official Pelican GH Pages action at
 ## https://github.com/getpelican/pelican/blob/main/.github/workflows/github_pages.yml
 
 name: Deploy Pelican site to GH Pages
@@ -13,75 +13,108 @@ on:
 
   workflow_dispatch:
 
+
+### This will be really convenient if/when actions supports changing working dir
+###jobs:
+###  deploy:
+###    uses: "getpelican/pelican/.github/workflows/github_pages.yml@main"
+###    # Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
+###    permissions:
+###      contents: read
+###      pages: write
+###      id-token: write
+###    with:
+###      settings: "publishconf.py"
+###      python: "3.9"
+###      # TODO: update when officially switching to community-managed page
+###      siteurl: "https://test.idris-lang.org/"
+###      requirements: "-r requirements.txt"
+###      # FIXME: remove when workflow is no longer bitrotted
+###      deploy: false
+
+### For now, we will just copy the Pelican CI and cd "manually"
+
 # c.f. https://docs.github.com/en/actions/how-tos/writing-workflows/choosing-what-your-workflow-does/setting-a-default-shell-and-working-directory
 defaults:
   run:
     shell: bash
     working-directory: ./src
 
-jobs:
-  deploy:
-    uses: "getpelican/pelican/.github/workflows/github_pages.yml@main"
-    # Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
-    permissions:
-      contents: read
-      pages: write
-      id-token: write
-    with:
-      settings: "./src/publishconf.py"
-      python: "3.9"
-      # TODO: update when officially switching to community-managed page
-      siteurl: "https://test.idris-lang.org/"
-      requirements: "-r ./src/requirements.txt"
-      # FIXME: remove when workflow is no longer bitrotted
-      deploy: false
-
+env:
+  SETTINGS: "publishconf.py"
+  PYTHON: "3.9"
+  # TODO: update when officially switching to community-managed page
+  SITEURL: "https://test.idris-lang.org/"
+  REQUIREMENTS: "-r requirements.txt"
+  # FIXME: remove when workflow is no longer bitrotted
+  DEPLOY: false
 
 # Allow one concurrent deployment
 concurrency:
   group: "pages"
   cancel-in-progress: true
 
-### defaults:
-###   run:
-###     shell: bash
-###
-### jobs:
-###   build:
-###     runs-on: ubuntu-latest
-###
-###     steps:
-###       - name: Checkout source
-###         uses: actions/checkout@v3
-###
-###       - name: Setup Python
-###         uses: actions/setup-python@v4
-###         with:
-###           python-version: "3.9"
-###           cache: 'pip'
-###
-###       - name: Install Pelican
-###         run: pip install pelican markdown
-###
-###       - name: Build site using Pelican
-###         run: |
-###           cd src
-###           pelican content -s publishconf.py
-###           cd ..
-###
-###       - name: Upload site
-###         uses: actions/upload-pages-artifact@v1
-###         with:
-###           path: ./src/output
-###
-###   deploy:
-###     environment:
-###       name: github-pages
-###       url: ${{ steps.deployment.outputs.page_url }}
-###     runs-on: ubuntu-latest
-###     needs: build
-###     steps:
-###       - name: Deploy to GH Pages
-###         id: deployment
-###         uses: actions/deploy-pages@v1
+# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ env.PYTHON }}
+      - name: Checkout theme
+        if: ${{ env.THEME }}
+        run: git clone '${{ env.THEME }}' .theme
+      - name: Configure GitHub Pages
+        id: pages
+        uses: actions/configure-pages@v5
+      - name: Install requirements
+        run: pip install ${{ env.REQUIREMENTS }}
+      - name: Build Pelican site
+        shell: python
+        run: |
+          import subprocess
+
+          cmd = "pelican"
+          cmd += " --settings ${{ env.SETTINGS }}"
+          cmd += " --extra-settings"
+          cmd += """ SITEURL='"${{ env.SITEURL || steps.pages.outputs.base_url }}"'"""
+          cmd += """ FEED_DOMAIN='"${{ env.FEED_DOMAIN || steps.pages.outputs.base_url }}"'"""
+          cmd += " --output ${{ env.OUTPUT_PATH }}"
+
+          if "${{ env.THEME }}":
+              cmd += " --theme-path .theme"
+
+          subprocess.run(cmd, shell=True, check=True)
+      - name: Fix permissions
+        run: |
+          chmod -c -R +rX "${{ env.OUTPUT_PATH }}" | while read line; do
+            echo "::warning title=Invalid file permissions automatically fixed::$line"
+          done
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: ${{ env.OUTPUT_PATH || "output/" }}
+  deploy:
+    concurrency:
+      group: "pages"
+      cancel-in-progress: false
+    if: ${{ env.DEPLOY }}
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4