History of HubBackend::caller 2 changes

In crates/hub/src/protocol.rs, lines 51–70 on 19bb31ff1f5c8ff9ba3d735ab52243e72182fbad1cfd352eaf986d65c9daee12. Every change that wrote or deleted one of these lines, or deleted a line from between them. Exact, because each line keeps its identity across edits; edits elsewhere in the file are not here. Also: oxy log -L 51,70:crates/hub/src/protocol.rs.