History of Mark::rings 2 changes

In crates/backdrop/src/mark.rs, lines 67–71 on 85ec74fd82d8075b2e48d1383547cc3a18886327bb29b28f08c58d8a29929fad. 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 67,71:crates/backdrop/src/mark.rs.