History of Pool::keep 4 changes

In crates/flow/src/cache.rs, lines 230–265 on 248cdef759aeb34d950d17663340b65699febb3da1996cf8c790322ca6536422. 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.