History of Mark::rings 2 changes

In crates/backdrop/src/mark.rs, lines 67–71 on d1bf2d698777c051db9fb656317446513bc0b8ba3c7aadf3c65891c4a96a52c3. 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.