Function attach_source 

pub fn attach_source(
    store: &mut Store,
    slug: &str,
    root_path: Option<&str>,
    source: &mut dyn SyncSource,
    ts: &str,
    config: &Config,
) -> Result<AttachResult>

ensure_repo, then for every enumerated entry fetch and ingest — with the reconciling resolver when identity is inferred, the plain re-mint ingest otherwise (§9) — counting files and whether all converged. A member whose fetch returns None is skipped.