Function intraline 

pub fn intraline(old: &str, new: &str) -> (Vec<Range<usize>>, Vec<Range<usize>>)

Byte ranges (into each input) that differ between the two lines.

Returns (old_emphasis, new_emphasis). Adjacent ranges are merged.

use diffler_core::diff::intraline;

let (old, new) = intraline("if x < y:", "if x <= y:");
assert!(old.is_empty());
assert_eq!(new, vec![6..7]);