pub async fn dag_export(cid_str: &str, output: Option<&Path>) -> Result<()>Expand description
Export a DAG sub-graph as a CAR v1 stream.
When output is None, the CAR bytes are written to stdout.
Traversal is breadth-first; only locally available blocks are included.
CAR v1 format (simplified, no compression):
<varint: header-len> <dag-cbor-header> <blocks…>Each block:
<varint: cid-len + data-len> <cid-bytes> <data-bytes>