Function fsck_pack_range 

pub fn fsck_pack_range(
    claim: &PackRangeClaim,
    audit: &PackRangeAudit<'_>,
) -> FsckReport

Check that a coalesced pack range is offset-canonical, gap-free, and — when the caller supplies them — digest-correct and manifest-covered.

This is the rule that keeps one physical range read from authorizing an unselected byte gap in a mixed-audience pack.