refactor: write one contributing text for both pages

tests/test_contributing_text.py

@@ -0,0 +1,35 @@
+"""CONTRIBUTING.md and the site's contributing page say the same thing.
+
+Two generators wrote the page and drifted: four steps to add a platform in
+the repository, five on the site, under two different titles.
+"""
+
+from __future__ import annotations
+
+import re
+import sys
+import unittest
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parent.parent
+sys.path.insert(0, str(REPO_ROOT / "scripts"))
+
+import generate_readme  # noqa: E402
+import generate_site  # noqa: E402
+
+
+def _normalized(text: str) -> str:
+    text = re.sub(r"\]\([^)]*\)", "](link)", text)
+    return "\n".join(text.splitlines()[1:]).replace("on this site", "on the documentation site")
+
+
+class OneContributingText(unittest.TestCase):
+    def test_repository_and_site_pages_match(self):
+        self.assertEqual(
+            _normalized(generate_readme.generate_contributing()),
+            _normalized(generate_site.generate_contributing()),
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()