History of unpack 2 changes

In crates/flow/src/checkpoint.rs, lines 109–164 on 0d663e91c598d7d2f8622364d706a06216b0a3e72062d9fbd8e972012c8aaf43. 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 109,164:crates/flow/src/checkpoint.rs.