feat: show line change counts in diff tabs

src/editor.rs

@@ -3381,9 +3381,11 @@ impl Editor {
     }
 
     pub fn tab_is_diff(&self, index: usize) -> bool {
-        self.tab_order
-            .get(index)
-            .is_some_and(|id| self.tab_diff(*id).is_some())
+        self.tab_diff_at(index).is_some()
+    }
+
+    pub(crate) fn tab_diff_at(&self, index: usize) -> Option<&DiffState> {
+        self.tab_diff(*self.tab_order.get(index)?)
     }
 
     pub(crate) fn tab_diff(&self, id: usize) -> Option<&DiffState> {