Function private_checks 

pub fn private_checks<'a, F: RepositoryFacts>(
    checks: &'a mut ShippedChecks<F>,
    index: &Path,
    object_directory: &Path,
    candidates: CandidateRequest,
) -> ShippedChecks<PrivateIndexFacts<&'a mut F>>

What: Rebuild the shipped checks over the private commit index: rule facts stay real, the candidates come from the private index against the recorded base. Why: The incumbent’s rules ask real Git about the real index, while the content policies read what the transaction corrects.

In TS you’d write (pseudocode):

const facts = createPrivateIndexFacts({ gitPath, cwd, indexPath, paths, baseRevision, objectDirectory });