Generalize View::object_selections into map

This allows using multiple distinct state histories. By default, all
history is also cleared any time a view's selection is set, unless
explicitly told to save the state. This way, we can have control over
when selection history is saved.

Author: dead10ck

helix-term/src/application.rs

@@ -221,10 +221,10 @@ impl Application {
                         // NOTE: this isn't necessarily true anymore. If
                         // `--vsplit` or `--hsplit` are used, the file which is
                         // opened last is focused on.
-                        let view_id = editor.tree.focus;
+                        let view = view_mut!(editor);
                         let doc = doc_mut!(editor, &doc_id);
                         let pos = Selection::point(pos_at_coords(doc.text().slice(..), pos, true));
-                        doc.set_selection(view_id, pos);
+                        doc.set_selection(view, pos);
                     }
                 }
                 editor.set_status(format!(