On 12/8/23 9:02 PM, Junio C Hamano wrote:

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* jc/diff-cached-fsmonitor-fix (2023-09-15) 3 commits
  - diff-lib: fix check_removed() when fsmonitor is active
  - Merge branch 'jc/fake-lstat' into jc/diff-cached-fsmonitor-fix
  - Merge branch 'js/diff-cached-fsmonitor-fix' into jc/diff-cached-fsmonitor-fix
  (this branch uses jc/fake-lstat.)

  The optimization based on fsmonitor in the "diff --cached"
  codepath is resurrected with the "fake-lstat" introduced earlier.

  It is unknown if the optimization is worth resurrecting, but in case...
  source: <xmqqr0n0h0tw.fsf@gitster.g>

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* jc/fake-lstat (2023-09-15) 1 commit
  - cache: add fake_lstat()
  (this branch is used by jc/diff-cached-fsmonitor-fix.)

  A new helper to let us pretend that we called lstat() when we know
  our cache_entry is up-to-date via fsmonitor.

  Needs review.
  source: <xmqqcyykig1l.fsf@gitster.g>

I think these look good.  And yes, it is better to insure that the
stat struct is always well-defined rather than sometimes uninitialized.


FWIW, in
f954c7b8ff3 (fsmonitor: never set CE_FSMONITOR_VALID on submodules, 
2022-05-26)
we try to never set the CE_FSMONITOR_VALID bit on submodules (because
status on a submodule is much more than just an lstat check on the
submodule root directory and we always should recursively ask Git to
compute the submodule's status).

I haven't had time to investigate, but I wonder if the original
complaint on `diff-lib` was due to another code path that allowed
the CE_FSMONITOR_VALID bit to get set on a submodule entry.

Jeff