Add doc comments

Author: Wilfred

src/diff/changes.rs

@@ -7,6 +7,9 @@ use crate::{
 
 #[derive(PartialEq, Eq, Clone, Copy)]
 pub(crate) enum ChangeKind<'a> {
+    /// This node is shallowly unchanged. For lists, this means that
+    /// the delimiters match, but there may still be some differences
+    /// in the children between LHS and RHS.
     Unchanged(&'a Syntax<'a>),
     ReplacedComment(&'a Syntax<'a>, &'a Syntax<'a>),
     ReplacedString(&'a Syntax<'a>, &'a Syntax<'a>),

src/display/hunks.rs

@@ -130,6 +130,11 @@ fn extract_lines(hunk: &Hunk) -> Vec<(Option<LineNumber>, Option<LineNumber>)> {
     relevant
 }
 
+/// If any hunks are sufficiently close that they have overlapping
+/// lines, merge them.
+///
+/// For example, given a hunk from lines 8-10 and a hunk from lines
+/// 12-15 with 5 context lines, combine the two hunks.
 pub(crate) fn merge_adjacent(
     hunks: &[Hunk],
     opposite_to_lhs: &DftHashMap<LineNumber, DftHashSet<LineNumber>>,