Merge branch 'tb/commit-graph-split-strategy'

"git commit-graph write" learned different ways to write out split
files.

* tb/commit-graph-split-strategy:
  Revert "commit-graph.c: introduce '--[no-]check-oids'"
  commit-graph.c: introduce '--[no-]check-oids'
  commit-graph.h: replace 'commit_hex' with 'commits'
  oidset: introduce 'oidset_size'
  builtin/commit-graph.c: introduce split strategy 'replace'
  builtin/commit-graph.c: introduce split strategy 'no-merge'
  builtin/commit-graph.c: support for '--split[=<strategy>]'
  t/helper/test-read-graph.c: support commit-graph chains

diff --cc builtin/commit-graph.c
Simple merge

diff --cc commit-graph.c
Simple merge

diff --cc oidset.h
Simple merge

diff --cc t/t5318-commit-graph.sh
Simple merge

diff --cc t/t5324-split-commit-graph.sh
Simple merge