Combine build.yml and github_pages.yml

Combine `build.yml` and `github_pages.yml` into a single workflow file.
Having `build.yml` be a separate workflow file that `github_pages.yml`
calls has two problems:

1. All the inputs (and their types, descriptions, defaults) have to be
   duplicated in the two workflow files.

2. The reference to `@main` in `uses: "getpelican/pelican/.github/workflows/build.yml@main"`
   in the `github_pages.yml` workflow makes development and testing
   awkward.

For example let's say you want to send a pull request that contains
changes to `build.yml` and that also requires changes to
`github_pages.yml` at the same time. The problem is that the
`github_pages.yml` on your PR branch will still contain the reference to
`build.yml` `@main` so if you try to test the branch's version of
`github_pages.yml` it'll call the version of `build.yml` from `main` not
from the PR branch and will fail.

This commit move the build job from `build.yml` into `github_pages.yml`
but makes the deploy job optional: it adds a `deploy` input and will
only run the deploy job if `deploy = true` is passed.

Previously a user could test their build without deploying it by calling
the separate `build.yml` workflow. Now they can do it by calling the
`github_pages.yml` workflow and passing `deploy=false`.

This commit also moves the `concurrency` stuff from the workflow level
to the deploy level: it's okay to have multiple build jobs running
concurrently, just not multiple deploy jobs.

.github/workflows/github_pages.yml

@@ -1,4 +1,4 @@
-# Workflow for publishing to GitHub Pages.
+# Workflow for building the site and (optionally) publishing it to GitHub Pages.
 name: Deploy to GitHub Pages
 on:
   workflow_call:
@@ -37,25 +37,63 @@ on:
         default: ""
         description: "The domain to be prepended to feed URLs (Pelican's FEED_DOMAIN setting). If not passed this will default to the URL of your GitHub Pages site, which is correct in most cases."
         type: string
+      deploy:
+        required: false
+        default: true
+        description: "Whether to deploy the site. If true then build the site and deploy it. If false then just test that the site builds successfully but don't deploy anything."
+        type: boolean
 permissions:
   contents: read
   pages: write
   id-token: write
-concurrency:
-  group: "pages"
-  cancel-in-progress: false
 jobs:
   build:
-    uses: "getpelican/pelican/.github/workflows/build.yml@main"
-    with:
-      settings: ${{ inputs.settings }}
-      requirements: ${{ inputs.requirements }}
-      output-path: ${{ inputs.output-path }}
-      theme: ${{ inputs.theme }}
-      python: ${{ inputs.python }}
-      siteurl: ${{ inputs.siteurl }}
-      feed_domain: ${{ inputs.feed_domain }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ inputs.python }}
+      - name: Checkout theme
+        if: ${{ inputs.theme }}
+        run: git clone '${{ inputs.theme }}' .theme
+      - name: Configure GitHub Pages
+        id: pages
+        uses: actions/configure-pages@v5
+      - name: Install requirements
+        run: pip install ${{ inputs.requirements }}
+      - name: Build Pelican site
+        shell: python
+        run: |
+          import subprocess
+
+          cmd = "pelican"
+          cmd += " --settings ${{ inputs.settings }}"
+          cmd += " --extra-settings"
+          cmd += """ SITEURL='"${{ inputs.siteurl || steps.pages.outputs.base_url }}"'"""
+          cmd += """ FEED_DOMAIN='"${{ inputs.feed_domain || steps.pages.outputs.base_url }}"'"""
+          cmd += " --output ${{ inputs.output-path }}"
+
+          if "${{ inputs.theme }}":
+              cmd += " --theme-path .theme"
+
+          subprocess.run(cmd, shell=True, check=True)
+      - name: Fix permissions
+        run: |
+          chmod -c -R +rX "${{ inputs.output-path }}" | while read line; do
+            echo "::warning title=Invalid file permissions automatically fixed::$line"
+          done
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: ${{ inputs.output-path }}
   deploy:
+    concurrency:
+      group: "pages"
+      cancel-in-progress: false
+    if: ${{ inputs.deploy }}
     environment:
       name: github-pages
       url: ${{ steps.deployment.outputs.page_url }}