Run yamllint and actionlint in CI

No issue closed: CI change requested by S01.

.gitea/workflows/ci.yml

@@ -1,7 +1,7 @@
-# Continuous integration for the squirrel census project: runs the pytest tests
-# on Python 3.13 for every push and pull request. Read by Gitea Actions (a
-# runner must be registered for the repository). It changes nothing outside the
-# repository and uses no secret. Decision: MIL-001 task "Add CI workflow".
+# Continuous integration for the squirrel census project: lints the YAML and
+# workflow files and runs the pytest tests on Python 3.13 for every push and
+# pull request. Read by Gitea Actions (a runner must be registered for the
+# repository). It changes nothing outside the repository and uses no secret. Decision: MIL-001 task "Add CI workflow".
 # Host: Gitea Actions; uses only github.* contexts, so it also runs on GitHub.
 
 name: Tests
@@ -42,5 +42,11 @@ jobs:
           .venv/bin/python -m pip install --upgrade "pip==${PIP_VERSION}"
           .venv/bin/python -m pip install -e ".[dev]"
 
+      - name: Lint the YAML files
+        run: .venv/bin/python -m yamllint -c .yamllint.yml .gitea .yamllint.yml
+
+      - name: Lint the workflow files
+        run: .venv/bin/actionlint .gitea/workflows/*.yml
+
       - name: Run the tests
         run: .venv/bin/python -m pytest

.yamllint.yml

@@ -6,6 +6,6 @@ rules:
     max: 100
   truthy:
     check-keys: false
-  # Git on Windows checks files out with CRLF; the repository blob has LF.
-  new-lines:
-    type: platform
+  # Line endings are normalised by git (LF in the repository, CRLF in some
+  # Windows checkouts), so the rule would fail on a local checkout only.
+  new-lines: disable

README.md

@@ -90,7 +90,8 @@ it is present.
 
 The workflow [`.gitea/workflows/ci.yml`][ci] runs for every push to `main` and for every
 pull request. It sets up Python 3.13, creates a `.venv`, upgrades `pip`, installs the
-project with `.[dev]` and runs `python -m pytest`. It uses `github.*` contexts only, so
+project with `.[dev]`, lints the YAML and workflow files with `yamllint` and
+`actionlint`, and runs `python -m pytest`. It uses `github.*` contexts only, so
 it also runs on GitHub Actions.
 
 ## Build the source documentation