[PATCH v2 0/5] commit-graph: fsck zero/non-zero generation number fixes

Here's a small reroll of a series that I sent which expanded on a patch that Peff sent earlier in the thread to remove a section of unreachable code that was noticed by Coverity in the `verify_one_commit_graph()` function.

Everything is the same in the first three patches. The fourth patch is slightly modified to (in addition to flipping the conditional) extract the mixed zero/non-zero generation number checks out to its own function.

The fifth patch is new, and avoids repeatedly warning about mixed generation numbers by treating `generation_zero` as a bitfield.

Thanks as always for your review!

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

Taylor Blau (4):
  commit-graph: introduce `commit_graph_generation_from_graph()`
  t/t5318-commit-graph.sh: test generation zero transitions during fsck
  commit-graph: invert negated conditional, extract to function
  commit-graph: avoid repeated mixed generation number warnings

 commit-graph.c          | 48 ++++++++++++++++++++++++++++++++---------
 t/t5318-commit-graph.sh | 32 +++++++++++++++++++++------
 2 files changed, 64 insertions(+), 16 deletions(-)

Range-diff against v1: 1: 6ea610f7d2 < -: ---------- commit-graph: invert negated conditional -: ---------- > 1: 701c198e19 commit-graph: introduce `commit_graph_generation_from_graph()` -: ---------- > 2: 9b9483893c commit-graph: verify swapped zero/non-zero generation cases -: ---------- > 3: 8679db3d0e t/t5318-commit-graph.sh: test generation zero transitions during fsck -: ---------- > 4: 32b5d69ebe commit-graph: invert negated conditional, extract to function -: ---------- > 5: b82b15ebc8 commit-graph: avoid repeated mixed generation number warnings