Allow unfolding deleted buffers in project diff w/ keyboard (#25835)

Release Notes:

- N/A

crates/editor/src/editor.rs

@@ -13018,11 +13018,11 @@ impl Editor {
             self.fold_creases(to_fold, true, window, cx);
         } else {
             let multi_buffer_snapshot = self.buffer.read(cx).snapshot(cx);
-
+            let buffer_ids = self
-            let buffer_ids: HashSet<_> = multi_buffer_snapshot
+                .selections
-                .ranges_to_buffer_ranges(self.selections.disjoint_anchor_ranges())
+                .disjoint_anchor_ranges()
-                .map(|(snapshot, _, _)| snapshot.remote_id())
+                .flat_map(|range| multi_buffer_snapshot.buffer_ids_for_range(range))
-                .collect();
+                .collect::<HashSet<_>>();
             for buffer_id in buffer_ids {
                 self.fold_buffer(buffer_id, cx);
             }
@@ -13195,10 +13195,11 @@ impl Editor {
             self.unfold_ranges(&ranges, true, true, cx);
         } else {
             let multi_buffer_snapshot = self.buffer.read(cx).snapshot(cx);
-            let buffer_ids: HashSet<_> = multi_buffer_snapshot
+            let buffer_ids = self
-                .ranges_to_buffer_ranges(self.selections.disjoint_anchor_ranges())
+                .selections
-                .map(|(snapshot, _, _)| snapshot.remote_id())
+                .disjoint_anchor_ranges()
-                .collect();
+                .flat_map(|range| multi_buffer_snapshot.buffer_ids_for_range(range))
+                .collect::<HashSet<_>>();
             for buffer_id in buffer_ids {
                 self.unfold_buffer(buffer_id, cx);
             }

crates/multi_buffer/src/multi_buffer.rs

@@ -3541,7 +3541,9 @@ impl MultiBufferSnapshot {
         cursor.seek(&range.start);
         std::iter::from_fn(move || {
             let region = cursor.region()?;
-            if region.range.start >= range.end {
+            if region.range.start > range.end
+                || region.range.start == range.end && region.range.start > range.start
+            {
                 return None;
             }
             cursor.next_excerpt();

crates/multi_buffer/src/multi_buffer_tests.rs

@@ -2035,6 +2035,25 @@ fn test_diff_hunks_with_multiple_excerpts(cx: &mut TestAppContext) {
         ]
     );
 
+    let buffer_ids_by_range = [
+        (Point::new(0, 0)..Point::new(0, 0), &[id_1] as &[_]),
+        (Point::new(0, 0)..Point::new(2, 0), &[id_1]),
+        (Point::new(2, 0)..Point::new(2, 0), &[id_1]),
+        (Point::new(3, 0)..Point::new(3, 0), &[id_1]),
+        (Point::new(8, 0)..Point::new(9, 0), &[id_1]),
+        (Point::new(8, 0)..Point::new(10, 0), &[id_1, id_2]),
+        (Point::new(9, 0)..Point::new(9, 0), &[id_2]),
+    ];
+    for (range, buffer_ids) in buffer_ids_by_range {
+        assert_eq!(
+            snapshot
+                .buffer_ids_for_range(range.clone())
+                .collect::<Vec<_>>(),
+            buffer_ids,
+            "buffer_ids_for_range({range:?}"
+        );
+    }
+
     assert_position_translation(&snapshot);
     assert_line_indents(&snapshot);