Update CI, in line with gitdb

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+- package-ecosystem: "github-actions"
+  directory: "/"
+  schedule:
+      interval: "weekly"

.github/workflows/pythonpackage.yml

@@ -16,19 +16,23 @@ jobs:
     strategy:
       matrix:
         python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12"]
+        include:
+          - experimental: false
+          - python-version: "3.12"
+            experimental: true
+    continue-on-error: ${{ matrix.experimental }}
 
     steps:
     - uses: actions/checkout@v4
-      with:
-        fetch-depth: 1000
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
-        allow-prereleases: true
-    - name: Install dependencies
+        allow-prereleases: ${{ matrix.experimental }}
+    - name: Install project
       run: |
         python -m pip install --upgrade pip
+        pip install .
     - name: Lint with flake8
       run: |
         pip install flake8