migrate dead hg.python.org release notes URLs to GitHub

apps/downloads/migrations/0016_release_notes_url_hg_to_github.py

@@ -0,0 +1,51 @@
+"""Rewrite dead hg.python.org release notes URLs to their GitHub equivalents."""
+
+import re
+
+from django.db import migrations
+
+HG_URL_RE = re.compile(r"^https?://hg\.python\.org/cpython/(?:raw-)?file/(?P<ref>[^/]+)/(?P<path>.+)$")
+GITHUB_BLOB_URL = "https://github.com/python/cpython/blob/{ref}/{path}"
+
+# Mercurial changesets do not exist in git; map the ones stored in production
+# to the git ref for the same release.
+HG_CHANGESET_TO_GIT_REF = {
+    "15fc83c505e3": "b34ba3f174ced8b6534888179b2f22e0f006c26e",  # 2.3 (no v2.3 tag in git)
+    "e32e3a9f3902": "v2.7.7rc1",
+    "80ccce248ba2": "v2.7.10rc1",
+    "15c95b7d81dc": "v2.7.10",
+    "82dd9545bd93": "v2.7.11rc1",
+    "53d30ab403f1": "v2.7.11",
+}
+
+
+def github_url_for(hg_url):
+    match = HG_URL_RE.match(hg_url)
+    if match is None:
+        return None
+    ref = match["ref"]
+    if not ref.startswith("v"):
+        ref = HG_CHANGESET_TO_GIT_REF.get(ref)
+        if ref is None:
+            return None
+    return GITHUB_BLOB_URL.format(ref=ref, path=match["path"])
+
+
+def rewrite_hg_release_notes_urls(apps, schema_editor):
+    Release = apps.get_model("downloads", "Release")
+    db_alias = schema_editor.connection.alias
+    releases = Release.objects.using(db_alias).filter(release_notes_url__contains="hg.python.org")
+    for release in releases:
+        url = github_url_for(release.release_notes_url)
+        if url is not None:
+            Release.objects.using(db_alias).filter(pk=release.pk).update(release_notes_url=url)
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("downloads", "0015_releasefile_python_dot_org_urls"),
+    ]
+
+    operations = [
+        migrations.RunPython(rewrite_hg_release_notes_urls, migrations.RunPython.noop),
+    ]