In proposed change editors, apply diff hunks in batches (#18841)

Release Notes:

- N/A

crates/editor/src/editor.rs

@@ -6213,14 +6213,22 @@ impl Editor {
     fn apply_selected_diff_hunks(&mut self, _: &ApplyDiffHunk, cx: &mut ViewContext<Self>) {
         let snapshot = self.buffer.read(cx).snapshot(cx);
         let hunks = hunks_for_selections(&snapshot, &self.selections.disjoint_anchors());
+        let mut ranges_by_buffer = HashMap::default();
         self.transact(cx, |editor, cx| {
             for hunk in hunks {
                 if let Some(buffer) = editor.buffer.read(cx).buffer(hunk.buffer_id) {
-                    buffer.update(cx, |buffer, cx| {
-                        buffer.merge_into_base(Some(hunk.buffer_range.to_offset(buffer)), cx);
-                    });
+                    ranges_by_buffer
+                        .entry(buffer.clone())
+                        .or_insert_with(Vec::new)
+                        .push(hunk.buffer_range.to_offset(buffer.read(cx)));
                 }
             }
+
+            for (buffer, ranges) in ranges_by_buffer {
+                buffer.update(cx, |buffer, cx| {
+                    buffer.merge_into_base(ranges, cx);
+                });
+            }
         });
     }