fix(code): reject cross-root credential aliases

Author: danny-avila

packages/code/src/github.test.ts

@@ -511,6 +511,11 @@ test('checkout routing follows nested repositories only inside an admitted root'
     await gitHubRepositoryForCommand(escaped, admitted, 'checkout'),
     undefined,
   );
+  admitted.set(outside, 'acme/outside');
+  assert.equal(
+    await gitHubRepositoryForCommand(escaped, admitted, 'checkout'),
+    undefined,
+  );
   assert.equal(
     await gitHubRepositoryForCommand(nested, admitted, 'checkout', 'github.example.test'),
     undefined,

packages/code/src/github.ts

@@ -181,7 +181,9 @@ export async function gitHubRepositoryForCommand(
     signal?.throwIfAborted();
     return undefined;
   }
-  if (!admittedRepositoryEntry(canonicalCwd, repositories)) return undefined;
+  if (admittedRepositoryEntry(canonicalCwd, repositories)?.[0] !== admitted[0]) {
+    return undefined;
+  }
   return gitHubRepositoryForDirectory(canonicalCwd, host, signal);
 }