Function index_with_gc 

pub async fn index_with_gc(
    root: &Path,
    src: &Path,
    repo: &str,
    view: &str,
    gc_after: bool,
) -> Result<(IndexSummary, Option<GcSummary>)>

index the (repo, view) view, then — when gc_after — sweep orphaned slices. The opt-in post-index trigger of gonzalo#104: the sweep runs only after a successful index and always goes through gc, which marks against every live view’s manifest (never a per-view subset), so a slice the just- indexed view dropped but another view still references is preserved.