Make buffer search aware of search direction (#24974)

This solves a couple of issues with Vim search by making the search
buffer and `SearchableItem` aware of the direction of the search. If
`SearchOptions::BACKWARDS` is set, all operations will be reversed. By
making `SearchableItem` aware of the direction, the correct active match
can be selected when searching backward.

Fixes #22506. This PR does not fix the last problem in that issue, but
that one is also tracked in #8049.

Release Notes:

- Fixes incorrect behavior of backward search in Vim mode

crates/search/src/buffer_search.rs

@@ -1306,7 +1306,16 @@ impl BufferSearchBar {
         done_rx
     }
 
+    fn reverse_direction_if_backwards(&self, direction: Direction) -> Direction {
+        if self.search_options.contains(SearchOptions::BACKWARDS) {
+            direction.opposite()
+        } else {
+            direction
+        }
+    }
+
     pub fn update_match_index(&mut self, window: &mut Window, cx: &mut Context<Self>) {
+        let direction = self.reverse_direction_if_backwards(Direction::Next);
         let new_index = self
             .active_searchable_item
             .as_ref()
@@ -1314,7 +1323,7 @@ impl BufferSearchBar {
                 let matches = self
                     .searchable_items_with_matches
                     .get(&searchable_item.downgrade())?;
-                searchable_item.active_match_index(matches, window, cx)
+                searchable_item.active_match_index(direction, matches, window, cx)
             });
         if new_index != self.active_match_index {
             self.active_match_index = new_index;

crates/search/src/project_search.rs

@@ -1240,6 +1240,7 @@ impl ProjectSearchView {
     fn update_match_index(&mut self, cx: &mut Context<Self>) {
         let results_editor = self.results_editor.read(cx);
         let new_index = active_match_index(
+            Direction::Next,
             &self.entity.read(cx).match_ranges,
             &results_editor.selections.newest_anchor().head(),
             &results_editor.buffer().read(cx).snapshot(cx),

crates/search/src/search.rs

@@ -47,6 +47,8 @@ bitflags! {
         const CASE_SENSITIVE = 0b010;
         const INCLUDE_IGNORED = 0b100;
         const REGEX = 0b1000;
+        /// If set, reverse direction when finding the active match
+        const BACKWARDS = 0b10000;
     }
 }