commit 6172f1c88f8fab8781f65d72d331d79cd1258d98
from: Jelmer Vernooij <jelmer@jelmer.uk>
date: Wed Apr 05 19:06:15 2023 UTC

Handle missing object

commit - 3fdec683ac6626aac79b13bdfa09114d21917eac
commit + 6172f1c88f8fab8781f65d72d331d79cd1258d98
blob - 58192fae475ba1c8c1ede617d58328a5ec56e778
blob + 870fe8cfc661a4cff5773c09ace9e502c0004699
--- dulwich/pack.py
+++ dulwich/pack.py
@@ -1387,7 +1387,8 @@ class DeltaChainIterator(Generic[T]):
             except KeyError:
                 if not allow_missing:
                     raise
-            todo.add(off)
+            else:
+                todo.add(off)
         done = set()
         while todo:
             off = todo.pop()