Compare the additional properties on headlines.

src/compare/compare_field.rs

@@ -32,6 +32,26 @@ pub(crate) enum ComparePropertiesResult<'b, 's> {
     DiffEntry(DiffEntry<'b, 's>),
 }
 
+impl<'b, 's> ComparePropertiesResult<'b, 's> {
+    pub(crate) fn apply(
+        self,
+        child_status: &mut Vec<DiffEntry<'b, 's>>,
+        this_status: &mut DiffStatus,
+        message: &mut Option<String>,
+    ) {
+        match self {
+            ComparePropertiesResult::NoChange => {}
+            ComparePropertiesResult::SelfChange(new_status, new_message) => {
+                *this_status = new_status;
+                *message = new_message
+            }
+            ComparePropertiesResult::DiffEntry(diff_entry) => child_status.push(diff_entry),
+        }
+
+        // foo
+    }
+}
+
 /// Do no comparison.
 ///
 /// This is for when you want to acknowledge that a field exists in the emacs token, but you do not have any validation for it when using the compare_properties!() macro. Ideally, this should be kept to a minimum since this represents untested values.