Squash doc into a single commit in gh-pages

Avoid long list of unreadable and not very relevant commits on gh-pages
branch.

.github/workflows/deploy-doc.yml

@@ -51,7 +51,8 @@ jobs:
           branch: gh-pages # The branch the action should deploy to.
           folder: ${{ inputs.doc-path }} # The folder the action should deploy.
           target-folder: /${{ inputs.doc-version }} # The folder the action should deploy to.
-          commit-message: publish documentation for ${{ inputs.doc-version }}
+          commit-message: publish documentation
+          single-commit: true
 
   update-doc-versions:
     # update doc versions index if the doc has been deployed
@@ -62,6 +63,8 @@ jobs:
         with:
           ref: gh-pages
       - uses: actions/setup-python@v4
+        with:
+          python-version: "3.10"
       - name: Generate versions.json
         shell: python3 {0}
         run: |
@@ -72,16 +75,15 @@ jobs:
           versions = sorted((item.name for item in cwd.iterdir()
                              if item.is_dir() and not item.name.startswith('.')),
                             reverse=True)
-          target_dir = Path('gh-pages')
-          target_dir.mkdir(parents=True)
-          target_file = target_dir / 'versions.json'
+          target_file = Path('versions.json')
           with target_file.open('w') as f:
               json.dump(versions, f)
       - name: Commit versions.json
-        uses: JamesIves/github-pages-deploy-action@v4
-        with:
-          branch: gh-pages # The branch the action should deploy to.
-          folder: gh-pages # The folder the action should deploy.
-          target-folder: / # The folder the action should deploy to.
-          commit-message: update versions.json
-          clean: false  # do not remove other files (including whole doc versions)
+        shell: bash
+        run: |
+          # Commit versions.json and squash it with previous commit
+          git config user.name "Actions"
+          git config user.email "[email protected]"
+          git add versions.json
+          git commit --amend --no-edit
+          git push -f origin gh-pages