Clone fold and selection state correctly when splitting an editor

crates/editor/src/display_map.rs

@@ -3,7 +3,7 @@ mod fold_map;
 mod tab_map;
 mod wrap_map;
 
-use crate::{Anchor, MultiBuffer, MultiBufferSnapshot, ToOffset, ToPoint};
+use crate::{Anchor, AnchorRangeExt, MultiBuffer, MultiBufferSnapshot, ToOffset, ToPoint};
 use block_map::{BlockMap, BlockPoint};
 use collections::{HashMap, HashSet};
 use fold_map::FoldMap;
@@ -97,6 +97,15 @@ impl DisplayMap {
         }
     }
 
+    pub fn set_state(&mut self, other: &DisplaySnapshot, cx: &mut ModelContext<Self>) {
+        self.fold(
+            other
+                .folds_in_range(0..other.buffer_snapshot.len())
+                .map(|fold| fold.to_offset(&other.buffer_snapshot)),
+            cx,
+        );
+    }
+
     pub fn fold<T: ToOffset>(
         &mut self,
         ranges: impl IntoIterator<Item = Range<T>>,