Function serve_with_selected_pack 

pub fn serve_with_selected_pack<R: Repository + ?Sized, W: Write>(
    repository: &ValidatedRepository<'_, '_, R>,
    request: Request<'_>,
    storage: &mut SelectionStorage<'_>,
    output: &mut W,
    write_selected: impl FnOnce(&[usize], &mut [u8], &mut PackOutput<'_, W>) -> Result<()>,
) -> Result<Response>

Serve selected requests using a trusted host’s raw-pack writer. Routing, authorization and bounded selection are identical to serve_with_selection. The writer runs once only when a pack is needed, including an empty selected set, and must emit exactly indices from this same stable repository. ACK-only rounds and shallow probes never invoke it. Its sink applies the current request’s sideband framing; cache only the raw PACK bytes.

Use cache::selected::write with Selection::Indices(indices) to integrate verified caller-owned caches. Authorization and selection precede every hit. Control packets may already be written when the writer fails: discard the entire output on any error. Buffer the response before sending HTTP success, or close the transport on a late failure. The writer retains no references after this synchronous call, and a failure emits no successful terminator.