Pipeline setup with Dockerfile

.gitea/workflows/ci.yml

@@ -9,16 +9,16 @@ on:
 jobs:
   lint:
     runs-on: ubuntu-latest
+    # Custom image (see .gitea/ci-image/Dockerfile): the official
+    # sagemath/sagemath image is amd64-only and this runner is arm64, and
+    # ruff/pytest are baked in here so jobs don't reinstall them every run.
     container:
-      image: sagemath/sagemath:10.4
+      image: gitea.piribauer.ch/julian/sage-ci:latest
 
     steps:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Install ruff
-        run: sage --pip install ruff
-
       - name: Preparse .sage files
         # Turns each *.sage file into real Python (*.sage.py) so ruff can
         # parse it, and prepends the `from sage.all import *` that `sage`
@@ -40,14 +40,11 @@ jobs:
     runs-on: ubuntu-latest
     needs: lint
     container:
-      image: sagemath/sagemath:10.4
+      image: gitea.piribauer.ch/julian/sage-ci:latest
 
     steps:
       - name: Checkout
         uses: actions/checkout@v4
 
-      - name: Install pytest
-        run: sage --pip install pytest
-
       - name: Run tests
         run: sage --python -m pytest tests/