Merge branch 'kk/commit-graph-topo-levels-fix'

The 'topo_levels' slab was propagated only to the topmost layer of a split commit-graph chain, causing topological levels for commits in base layers to be recomputed during incremental writes. This has been corrected. * kk/commit-graph-topo-levels-fix: commit-graph: propagate topo_levels slab to all chain layers commit-graph: add trace2 instrumentation for generation DFS