Update default vim substitute command behavior and add support for 'g' flag (#28138)

This Pull Request updates the default behavior of the substitute (`s`)
command in vim mode to only replace the next match by default, instead
of all, and replace all matches only when the `g` flag is provided,
making it more similar to NeoVim's behavior.

In order to achieve this, the following changes were introduced:

- Update `BufferSearchBar::replace_next` to be a public method, so it
can be called from `Vim::replace_command` .
- Update the `Replacement::parse` to set the `should_replace_all` field
to `false` by default, and only set it to `true` if the `'g'` flag is
present in the query.
- Add support for when the `Replacement.should_replace_all` is set to
`false` in `Vim::replace_command`, so as to have it only replace the
next occurrence instead of all occurrences in the line.
- Introduce `BufferSearchBar::select_first_match` so as to activate the
first match on the line under the cursor.

Closes #24450 

Release Notes:

- Improved vim's substitute command so as to only replace the first
match by default, and replace all matches if the `'g'` flag is provided

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/vim/src/normal/search.rs

@@ -445,6 +445,8 @@ impl Vim {
         }
         let vim = cx.entity().clone();
         pane.update(cx, |pane, cx| {
+            let mut options = SearchOptions::REGEX;
+
             let Some(search_bar) = pane.toolbar().read(cx).item_of_type::<BufferSearchBar>() else {
                 return;
             };
@@ -453,7 +455,6 @@ impl Vim {
                     return None;
                 }
 
-                let mut options = SearchOptions::REGEX;
                 if replacement.is_case_sensitive {
                     options.set(SearchOptions::CASE_SENSITIVE, true)
                 }
@@ -468,6 +469,11 @@ impl Vim {
                         search_bar.is_contains_uppercase(&search),
                     );
                 }
+
+                if !replacement.should_replace_all {
+                    options.set(SearchOptions::ONE_MATCH_PER_LINE, true);
+                }
+
                 search_bar.set_replacement(Some(&replacement.replacement), cx);
                 Some(search_bar.search(&search, Some(options), window, cx))
             });
@@ -476,29 +482,35 @@ impl Vim {
             cx.spawn_in(window, async move |_, cx| {
                 search.await?;
                 search_bar.update_in(cx, |search_bar, window, cx| {
-                    if replacement.should_replace_all {
-                        search_bar.select_last_match(window, cx);
-                        search_bar.replace_all(&Default::default(), window, cx);
-                        cx.spawn(async move |_, cx| {
-                            cx.background_executor()
-                                .timer(Duration::from_millis(200))
-                                .await;
-                            editor
-                                .update(cx, |editor, cx| editor.clear_search_within_ranges(cx))
-                                .ok();
-                        })
-                        .detach();
-                        vim.update(cx, |vim, cx| {
-                            vim.move_cursor(
-                                Motion::StartOfLine {
-                                    display_lines: false,
-                                },
-                                None,
-                                window,
-                                cx,
-                            )
-                        });
-                    }
+                    search_bar.select_last_match(window, cx);
+                    search_bar.replace_all(&Default::default(), window, cx);
+
+                    cx.spawn(async move |_, cx| {
+                        cx.background_executor()
+                            .timer(Duration::from_millis(200))
+                            .await;
+                        editor
+                            .update(cx, |editor, cx| editor.clear_search_within_ranges(cx))
+                            .ok();
+                    })
+                    .detach();
+                    vim.update(cx, |vim, cx| {
+                        vim.move_cursor(
+                            Motion::StartOfLine {
+                                display_lines: false,
+                            },
+                            None,
+                            window,
+                            cx,
+                        )
+                    });
+
+                    // Disable the `ONE_MATCH_PER_LINE` search option when finished, as
+                    // this is not properly supported outside of vim mode, and
+                    // not disabling it makes the "Replace All Matches" button
+                    // actually replace only the first match on each line.
+                    options.set(SearchOptions::ONE_MATCH_PER_LINE, false);
+                    search_bar.set_search_options(options, cx);
                 })?;
                 anyhow::Ok(())
             })
@@ -564,15 +576,16 @@ impl Replacement {
         let mut replacement = Replacement {
             search,
             replacement,
-            should_replace_all: true,
+            should_replace_all: false,
             is_case_sensitive: true,
         };
 
         for c in flags.chars() {
             match c {
-                'g' | 'I' => {}
+                'g' => replacement.should_replace_all = true,
                 'c' | 'n' => replacement.should_replace_all = false,
                 'i' => replacement.is_case_sensitive = false,
+                'I' => replacement.is_case_sensitive = true,
                 _ => {}
             }
         }