Merge branch 'ds/commit-graph-gen-v2-fixes'

Fixes to the way generation number v2 in the commit-graph files are (not) handled. * ds/commit-graph-gen-v2-fixes: commit-graph: declare bankruptcy on GDAT chunks commit-graph: fix generation number v2 overflow values commit-graph: start parsing generation v2 (again) commit-graph: fix ordering bug in generation numbers t5318: extract helpers to lib-commit-graph.sh test-read-graph: include extra post-parse info