Function difft::diff::sliders::slide_to_prev_node

fn slide_to_prev_node<'a>(
    nodes: &[&'a Syntax<'a>],
    change_map: &mut ChangeMap<'a>,
    start_idx: usize,
    end_idx: usize
)

If the previous node is unchanged, matches the end of the region, and has a smaller text distance, mark it as novel.

x UNCHANGED
y NOVEL <- start_idx

x NOVEL <- end_idx

After this function:

x NOVEL
y NOVEL

x UNCHANGED