History of Mark::rings 2 changes

In crates/backdrop/src/mark.rs, lines 67–71 on 3dd6582de0606a8aeb4dcb1bd92f41842aa12e787c93f090d64bdc409c40548c. 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.