History of Hub::checkpoint 1 change

In crates/flow/src/runner.rs, lines 253–266 on e3fb0e9b5e6bcee663a87da8d26d1e72d99442c6f4a119c324415dcdcaa920de. 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 253,266:crates/flow/src/runner.rs.