Function map_baseline_to_current 

pub fn map_baseline_to_current(index: &HunkIndex, row: u32) -> u32

Translate a baseline-side row to its current-side counterpart. Pure function of the published HunkIndex and the input row; exposed for direct unit testing without round-tripping through RowMapper. D.4.b-shape alias for map_between(index, 0, 1, row).