Function build_artifact_caches_batch 

pub fn build_artifact_caches_batch<E, F>(
    specs: &[ArtifactCacheSpec],
    populate: F,
) -> ArtifactCacheBatchReport<E>
where
    F: FnMut(usize, &ArtifactBuildTransaction) -> Result<(), E>,

Build every independent transactional artifact specification.

The callback runs only for misses and receives one live transaction at a time. Sequential acquisition avoids self-deadlock when entries share a coordination scope. Every result is retained, and a callback error aborts and synchronously cleans that transaction before the next entry begins.

This operation is not atomic across specifications. A caller requiring one all-or-nothing multi-output publication should declare those outputs on one ArtifactCacheSpec instead.