History of Pool::keep 4 changes

In crates/flow/src/cache.rs, lines 230–265 on 060d459ff6c6ed4b93b5cb59600f38b5663a8d44332f28b99c0f7918f1e8936c. 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 230,265:crates/flow/src/cache.rs.