Recover external repository renames through verified Forgejo redirects

Assistant: codex
Assistant-Model: gpt-6-astra
Assistant-Session: 01a070b5-4994-7271-bd8b-7c3dbcedec4b

api/services/forge_repository.py

@@ -12,7 +12,7 @@ import os
 from dataclasses import dataclass
 from pathlib import Path
 from typing import Protocol
-from urllib.parse import quote
+from urllib.parse import quote, urljoin
 
 import httpx
 
@@ -32,6 +32,14 @@ class ForgeRepositoryUnreadable(ForgeRepositoryError):
     pass
 
 
+class ForgeRepositoryRedirected(ForgeRepositoryUnreadable):
+    """Requested coordinate redirects; no credentials are forwarded."""
+
+    def __init__(self, source_url: str, location: str):
+        super().__init__("Forge repository coordinate redirects")
+        self.target_url = urljoin(source_url, location) if location else None
+
+
 class ForgeRepositoryConflict(ForgeRepositoryError):
     pass
 
@@ -106,6 +114,10 @@ class ForgejoRepositoryGateway:
         try:
             async with httpx.AsyncClient(timeout=timeout) as client:
                 response = await client.get(url, headers=self._headers(token))
+                if response.status_code in {301, 302, 303, 307, 308}:
+                    raise ForgeRepositoryRedirected(
+                        url, response.headers.get("location", "")
+                    )
                 if response.status_code == 404:
                     if token is None:
                         raise ForgeRepositoryUnreadable(