Fix panic folding in multi-buffers (#21511)

Closes #19054

Rename `max_buffer_row()` to `widest_line_number()` to (hopefully)
prevent
people assuming it means the same as `max_point().row`.

Release Notes:

- Fixed a panic when folding in a multibuffer

crates/vim/src/command.rs

@@ -136,7 +136,7 @@ pub fn register(editor: &mut Editor, cx: &mut ViewContext<Vim>) {
         vim.update_editor(cx, |vim, editor, cx| {
             let snapshot = editor.snapshot(cx);
             if let Ok(range) = action.range.buffer_range(vim, editor, cx) {
-                let end = if range.end < snapshot.max_buffer_row() {
+                let end = if range.end < snapshot.buffer_snapshot.max_row() {
                     Point::new(range.end.0 + 1, 0)
                 } else {
                     snapshot.buffer_snapshot.max_point()
@@ -436,9 +436,11 @@ impl Position {
                     .row
                     .saturating_add_signed(*offset)
             }
-            Position::LastLine { offset } => {
-                snapshot.max_buffer_row().0.saturating_add_signed(*offset)
-            }
+            Position::LastLine { offset } => snapshot
+                .buffer_snapshot
+                .max_row()
+                .0
+                .saturating_add_signed(*offset),
             Position::CurrentLine { offset } => editor
                 .selections
                 .newest_anchor()
@@ -448,7 +450,7 @@ impl Position {
                 .saturating_add_signed(*offset),
         };
 
-        Ok(MultiBufferRow(target).min(snapshot.max_buffer_row()))
+        Ok(MultiBufferRow(target).min(snapshot.buffer_snapshot.max_row()))
     }
 }
 

crates/vim/src/motion.rs

@@ -1866,7 +1866,7 @@ fn end_of_document(
     let new_row = if let Some(line) = line {
         (line - 1) as u32
     } else {
-        map.max_buffer_row().0
+        map.buffer_snapshot.max_row().0
     };
 
     let new_point = Point::new(new_row, point.column());

crates/vim/src/normal/yank.rs

@@ -154,9 +154,9 @@ impl Vim {
                 // contains a newline (so that delete works as expected). We undo that change
                 // here.
                 let is_last_line = linewise
-                    && end.row == buffer.max_buffer_row().0
+                    && end.row == buffer.max_row().0
                     && buffer.max_point().column > 0
-                    && start.row < buffer.max_buffer_row().0
+                    && start.row < buffer.max_row().0
                     && start == Point::new(start.row, buffer.line_len(MultiBufferRow(start.row)));
 
                 if is_last_line {

crates/vim/src/object.rs

@@ -724,7 +724,7 @@ fn indent(
 
     // Loop forwards until we find a non-blank line with less indent
     let mut end_row = row;
-    let max_rows = map.max_buffer_row().0;
+    let max_rows = map.buffer_snapshot.max_row().0;
     for next_row in (row + 1)..=max_rows {
         let indent = map.line_indent_for_buffer_row(MultiBufferRow(next_row));
         if indent.is_line_empty() {
@@ -958,13 +958,13 @@ pub fn start_of_paragraph(map: &DisplaySnapshot, display_point: DisplayPoint) ->
 /// The trailing newline is excluded from the paragraph.
 pub fn end_of_paragraph(map: &DisplaySnapshot, display_point: DisplayPoint) -> DisplayPoint {
     let point = display_point.to_point(map);
-    if point.row == map.max_buffer_row().0 {
+    if point.row == map.buffer_snapshot.max_row().0 {
         return map.max_point();
     }
 
     let is_current_line_blank = map.buffer_snapshot.is_line_blank(MultiBufferRow(point.row));
 
-    for row in point.row + 1..map.max_buffer_row().0 + 1 {
+    for row in point.row + 1..map.buffer_snapshot.max_row().0 + 1 {
         let blank = map.buffer_snapshot.is_line_blank(MultiBufferRow(row));
         if blank != is_current_line_blank {
             let previous_row = row - 1;