History of HubBackend::caller 2 changes

In crates/hub/src/protocol.rs, lines 51–70 on 1b3a00986a5af27d50714ac69a47297eb1eea88fa1017ee53bbc8d963d723859. 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.