History of Pool::keep 3 changes

In crates/flow/src/cache.rs, lines 207–241 on d59bf2389914322e07e723f658b4f56a42486cd520ce56b5138e2be319ca8cd4. 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 207,241:crates/flow/src/cache.rs.