commit-graph: propagate topo_levels slab to all chain layers

The topo_levels slab is only propagated to the topmost graph layer instead of all layers in the chain. Commits from lower layers appear to have no generation numbers, so the DFS re-walks the entire ancestry. Fix by making topo_levels visible to all layers, not just the first one. Signed-off-by: Kristofer Karlsson <krka@spotify.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

Kristofer Karlsson committed Jul 9, 2026 at 15:03 UTC 8ea36f63d8e63350325705afef885ae215e64217
2 files changed +2 -2
commit-graph.c
+1 -1
@@ -2610,7 +2610,7 @@ int write_commit_graph(struct odb_source *source,
2610
2611 g = prepare_commit_graph(ctx.r);
2612 for (struct commit_graph *chain = g; chain; chain = chain->base_graph)
2613 - g->topo_levels = &topo_levels;
2613 + chain->topo_levels = &topo_levels;
2614
2615 if (flags & COMMIT_GRAPH_WRITE_BLOOM_FILTERS)
2616 ctx.changed_paths = 1;
t/t5324-split-commit-graph.sh
+1 -1
@@ -718,7 +718,7 @@ test_expect_success 'write generation data chunk when commit-graph chain is repl
718 )
719 '
720
721 -test_expect_failure 'incremental write reads topo levels from all layers' '
721 +test_expect_success 'incremental write reads topo levels from all layers' '
722 git init topo-from-lower &&
723 (
724 cd topo-from-lower &&