Function difft::display::context::match_preceding_blanks

fn match_preceding_blanks(
    line_nums: &[(Option<LineNumber>, Option<LineNumber>)],
    lhs_lines: &[&str],
    rhs_lines: &[&str]
) -> Vec<(Option<LineNumber>, Option<LineNumber>)>

For every line number pair, if there are blank lines preceding the pair, add those blank lines to the vec.

This substantially improves alignment, leading to more readable diffs.

We don’t need to match blank lines following each pair. After matching up all the matching lines, we just display the remaining lines side-by-side regardless of content (see ensure_contiguous). If there are blank lines immediately following the pair, they will get aligned by this.