Merge branch 'jk/commit-graph-verify-fix'

Various fixes to "git commit-graph verify". * jk/commit-graph-verify-fix: commit-graph: report incomplete chains during verification commit-graph: tighten chain size check commit-graph: detect read errors when verifying graph chain t5324: harmonize sha1/sha256 graph chain corruption commit-graph: check mixed generation validation when loading chain file commit-graph: factor out chain opening function