Move selection helpers to SelectionCollection, add update_anchor_selections, add a number of invariant preserving mutation functions to the MutableSelectionCollection

crates/vim/src/insert.rs

@@ -13,9 +13,11 @@ pub fn init(cx: &mut MutableAppContext) {
 fn normal_before(_: &mut Workspace, _: &NormalBefore, cx: &mut ViewContext<Workspace>) {
     Vim::update(cx, |state, cx| {
         state.update_active_editor(cx, |editor, cx| {
-            editor.move_cursors(cx, |map, mut cursor, _| {
-                *cursor.column_mut() = cursor.column().saturating_sub(1);
-                (map.clip_point(cursor, Bias::Left), SelectionGoal::None)
+            editor.change_selections(true, cx, |s| {
+                s.move_cursors_with(|map, mut cursor, _| {
+                    *cursor.column_mut() = cursor.column().saturating_sub(1);
+                    (map.clip_point(cursor, Bias::Left), SelectionGoal::None)
+                });
             });
         });
         state.switch_mode(Mode::Normal, cx);