[PATCH 0/8] commit-graph: drop CHECK_OIDS, peel in callers

Hi,

These are a few patches to address [1] by getting rid of the
'COMMIT_GRAPH_WRITE_CHECK_OIDS' flag. A more complete discussion about
why we might want to get rid of that flag can be found in the second
patch, as well as in [1], but the basic gist is as follows:

  - It is often convenient to pipe the output of 'git for-each-ref' into
    'git commit-graph write --stdin-commits', but handling multi-layer
    tags is frustrating (at the very least, you have to peel them
    yourself in 'for-each-ref', incurring a higher-than-necessary cost
    outside of the commit-graph invocation)

  - It would be much more convenient if 'git commit-graph write
    --stdin-commits' ignored OIDs that peel down to non-commit objects
    silently, while still warning the caller about objects that (a)
    don't exist, or (b) invalid hash inputs (for e.g., "HEAD", or
    "refs/heads/foo").

  - By making this change, we are allowing *more* possible behaviors
    than in previous versions, and the only case that we are breaking
    (that 'git commit-graph write --stdin-commits' complains on
    non-commit OIDs) can be addressed by peeling outside of
    'commit-graph write' [2].

The first six patches move peeling refs out from the commit-graph
internals, and into the callers.

This has no impact on the '--stdin-commits' case, but is a potential
improvement for '--reachable', where it is more efficient to call
'peel_ref()' than 'lookup_commit_reference_gently()'. There is an
intermediate state (that is resolved in the final patch) where we can
have more than one progress meter (since the progress meter moved with
the perhaps-expensive operations out of the commit-graph internals,
too), but the final patch addresses this.

The last two patches lift the restriction on input to '--stdin-commits'
resolving to commit objects, instead making the behavior to silently
drop non-commit OIDs, and continue complain about invalid OIDs, and
valid-but-missing OIDs.

Finally, this topic isn't based on anything that isn't already in
'master', so I think the days of many tangle commit-graph topics are
behind us.

Thanks in advance for your review.

Thanks,
Taylor

Taylor Blau (8):
  commit-graph.c: extract 'refs_cb_data'
  commit-graph.c: show progress of finding reachable commits
  commit-graph.c: peel refs in 'add_ref_to_set'
  builtin/commit-graph.c: extract 'read_one_commit()'
  builtin/commit-graph.c: dereference tags in builtin
  commit-graph.c: simplify 'fill_oids_from_commits'
  t5318: reorder test below 'graph_read_expect'
  commit-graph: drop COMMIT_GRAPH_WRITE_CHECK_OIDS flag

 Documentation/git-commit-graph.txt |  6 ++-
 builtin/commit-graph.c             | 73 ++++++++++++++++++++----------
 commit-graph.c                     | 61 +++++++++++--------------
 commit-graph.h                     | 10 ++--
 t/t5318-commit-graph.sh            | 25 ++++++----
 5 files changed, 98 insertions(+), 77 deletions(-)

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2.26.0.113.ge9739cdccc