"Kristofer Karlsson via GitGitGadget" [off-list ref]
writes:

Changes since v2:

 * New patch 8/8: moved the min_generation termination check and the
   last_gen monotonicity assertion into paint_queue_get(), consolidating
   halt conditions. commit_graph_generation() is now called once per
   dequeued commit and shared across all checks.

 * Widened the generation-monotonicity BUG assertion to fire
   unconditionally, not only when min_generation is set. The side-exhaustion
   optimization depends on correct generation ordering, so the assertion
   should always be active. This is a behavior change: the BUG() now fires
   for any generation ordering violation, regardless of the caller.

 * Moved all halt conditions inside paint_queue_get() with the "pop first"
   form: pop, check, then decrement counters. This keeps the optimization
   commit's diff minimal (just inserting the new checks between pop and
   decrement).

 * Shortened the doc comment on paint_queue_get() to describe what it does
   rather than how. Inline comments on each return NULL explain the specific
   halt condition.

 * Replaced the manual commit-graph setup in the step-count test with
   run_all_modes, which now sets GIT_TRACE2_EVENT per mode and produces
   trace-mode-{none,full,half,no-gdat}.txt files.

 * Added a test_paint_down_steps helper for concise 4-mode step assertions
   with diagnostic output on mismatch (prints "expected X, got Y" instead of
   a silent grep failure).

 * Added step-count assertions to the single-walk edge-case tests:
   in_merge_bases_many:self, pending-stale, infinity-both-sides,
   mixed-finite-infinity.

 * Included step counts alongside wall-clock times in the benchmark tables.

I am getting this failure standalone, when applied on the same base
as where v2 was applied earlier.  For now I'll eject it from 'seen'.

expecting success of 6600.12 'get_merge_bases_many': 
        cat >input <<-\EOF &&
        A:commit-5-7
        X:commit-4-8
        X:commit-6-6
        X:commit-8-3
        EOF
        {
                echo "get_merge_bases_many(A,X):" &&
                git rev-parse commit-5-6 \
                              commit-4-7 | sort
        } >expect &&
        test_all_modes get_merge_bases_many

BUG: commit-reach.c:152: bad generation skip 9 > 8 at 772be737f220103f706a39013c0d115009feefec
not ok 12 - get_merge_bases_many
#
#               cat >input <<-\EOF &&
#               A:commit-5-7
#               X:commit-4-8