History of Mark::step 1 change

In crates/backdrop/src/mark.rs, lines 101–107 on a3ba7cc106738520cd2c50e68b9b31b1bcf006364c25c875770cc3541c6732bf. 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 101,107:crates/backdrop/src/mark.rs.