CI: attempt to fix the documentation build

.github/workflows/build.yml

@@ -1,6 +1,12 @@
 name: build
 
-on: [push, pull_request]
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
 
 jobs:
   fmt:
@@ -60,15 +66,3 @@ jobs:
         working-directory: ./python/docs
       - run: source ../venv/bin/activate && sphinx-build -M html . build
         working-directory: ./python/docs
-      - uses: actions/checkout@v2
-        with:
-          repository: oxigraph/oxigraph.github.io
-          path: website
-      - run: cp -r ./python/docs/build/html website/pyoxigraph/latest/
-      - run: |
-          git config user.name github-actions
-          git config user.email github-actions@github.com
-          git add .
-          git commit -m "Updates pyoxigraph documentation"
-          git push
-        working-directory: ./website

.github/workflows/doc.yml

@@ -0,0 +1,36 @@
+name: doc
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  python:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - run: rustup update
+      - uses: actions/setup-python@v2
+        with:
+          python-version: 3.8
+      - run: python -m venv python/venv
+      - run: source python/venv/bin/activate && pip install --upgrade pip maturin sphinx
+      - run: source venv/bin/activate && maturin develop
+        working-directory: ./python
+      - run: source ../venv/bin/activate && sphinx-build -M doctest . build
+        working-directory: ./python/docs
+      - run: source ../venv/bin/activate && sphinx-build -M html . build
+        working-directory: ./python/docs
+      - uses: actions/checkout@v2
+        with:
+          repository: oxigraph/oxigraph.github.io
+          path: website
+      - run: mkdir -p ./website/pyoxigraph/latest && cp -r ./python/docs/build/html/* ./website/pyoxigraph/latest/
+      - run: |
+          git config user.name github-actions
+          git config user.email github-actions@github.com
+          git add .
+          git diff-index --quiet HEAD || git commit -m "Updates pyoxigraph documentation"
+          git push
+        working-directory: ./website