Merge branch 'ak/corrected-commit-date'

The commit-graph learned to use corrected commit dates instead of
the generation number to help topological revision traversal.

* ak/corrected-commit-date:
  doc: add corrected commit date info
  commit-reach: use corrected commit dates in paint_down_to_common()
  commit-graph: use generation v2 only if entire chain does
  commit-graph: implement generation data chunk
  commit-graph: implement corrected commit date
  commit-graph: return 64-bit generation number
  commit-graph: add a slab to store topological levels
  t6600-test-reach: generalize *_three_modes
  commit-graph: consolidate fill_commit_graph_info
  revision: parse parent in indegree_walk_step()
  commit-graph: fix regression when computing Bloom filters

diff --cc commit-graph.c
Simple merge

diff --cc commit.c
Simple merge

diff --cc commit.h
Simple merge

diff --cc revision.c
Simple merge

diff --cc t/README
Simple merge

diff --cc t/t4216-log-bloom.sh
Simple merge

diff --cc t/t6404-recursive-merge.sh
Simple merge

diff --cc t/test-lib-functions.sh
Simple merge

diff --cc upload-pack.c
Simple merge