Add channel-aware release tooling and updater recovery

scripts/validate_release_remote.py

@@ -0,0 +1,70 @@
+#!/usr/bin/env python3
+"""Confirm that a Git remote points at the configured release repository."""
+
+from __future__ import annotations
+
+import argparse
+from pathlib import Path
+import re
+import sys
+from urllib.parse import unquote, urlsplit
+
+
+class RemoteValidationError(ValueError):
+	pass
+
+
+def repository_identity(value: str) -> tuple[str, str]:
+	if not value or any(character in value for character in "\r\n\0"):
+		raise RemoteValidationError("repository URL is empty or malformed")
+	scp = re.fullmatch(r"(?:[^@/:]+@)?([^/:]+):(.+)", value)
+	if scp is not None and "://" not in value:
+		return _remote_identity(scp.group(1), scp.group(2))
+	parts = urlsplit(value)
+	if parts.scheme in {"https", "http", "ssh", "git"}:
+		hostname = parts.hostname
+		if hostname is None:
+			raise RemoteValidationError("repository URL has no host")
+		host = hostname.casefold()
+		if parts.port is not None:
+			host += f":{parts.port}"
+		return _remote_identity(host, unquote(parts.path))
+	if parts.scheme == "file":
+		return "file", str(Path(unquote(parts.path)).expanduser().resolve())
+	if parts.scheme:
+		raise RemoteValidationError(f"unsupported repository URL scheme: {parts.scheme}")
+	return "file", str(Path(value).expanduser().resolve())
+
+
+def remote_matches(actual: str, expected: list[str]) -> bool:
+	actual_identity = repository_identity(actual)
+	return any(repository_identity(candidate) == actual_identity for candidate in expected)
+
+
+def _remote_identity(host: str, path: str) -> tuple[str, str]:
+	normalized = path.strip("/")
+	if normalized.endswith(".git"):
+		normalized = normalized[:-4]
+	if not host or not normalized or normalized.startswith("../"):
+		raise RemoteValidationError("repository URL has an invalid host or path")
+	return host.casefold(), normalized
+
+
+def main() -> int:
+	parser = argparse.ArgumentParser(description=__doc__)
+	parser.add_argument("actual")
+	parser.add_argument("expected", nargs="+")
+	arguments = parser.parse_args()
+	try:
+		if not remote_matches(arguments.actual, arguments.expected):
+			raise RemoteValidationError(
+				"configured Git remote does not point at the expected release repository"
+			)
+	except RemoteValidationError as exc:
+		print(f"Release remote validation failed: {exc}", file=sys.stderr)
+		return 1
+	return 0
+
+
+if __name__ == "__main__":
+	raise SystemExit(main())