[PATCH 0/4] commit-graph: fsck zero/non-zero generation number fixes

This series expands on a patch that Peff sent earlier in this thread to remove a section of unreachable code that was noticed by Coverity in the `verify_one_commit_graph()` function.

The first couple of patches addresses the main issue, which is that we couldn't verify ancient commit-graphs written with zero'd generation numbers. The third patch adds additional tests to ensure our coverage in this area is complete, and the final patch is a cleanup.

Thanks as always for your review.

Jeff King (1):
  commit-graph: verify swapped zero/non-zero generation cases

Taylor Blau (3):
  commit-graph: introduce `commit_graph_generation_from_graph()`
  t/t5318-commit-graph.sh: test generation zero transitions during fsck
  commit-graph: invert negated conditional

 commit-graph.c          | 23 ++++++++++++++++++-----
 t/t5318-commit-graph.sh | 18 ++++++++++++------
 2 files changed, 30 insertions(+), 11 deletions(-)