Simplify mark selection by making it based on position in list

And not on node index, which plays much less of a role there, if any

src/interactive/widgets/mark.rs

@@ -1,7 +1,6 @@
 use crate::interactive::{widgets::COLOR_MARKED_LIGHT, CursorDirection, EntryMark, EntryMarkMap};
 use dua::path_of;
 use dua::traverse::{Tree, TreeIndex};
-use itertools::Itertools;
 use std::borrow::Borrow;
 use termion::{event::Key, event::Key::*};
 use tui::{
@@ -16,7 +15,7 @@ use tui_react::{List, ListProps};
 
 #[derive(Default)]
 pub struct MarkPane {
- selected: Option<TreeIndex>,
+ selected: Option<usize>,
  marked: EntryMarkMap,
  list: List,
 }
@@ -71,18 +70,12 @@ impl MarkPane {
  .borders(Borders::ALL);
  let entry_in_view = self
  .selected
- .and_then(|selected| {
- marked
- .keys()
- .find_position(|&&index| index == selected)
- .map(|(pos, _)| pos)
- })
- .or_else(|| marked.keys().enumerate().last().map(|(pos, _)| pos));
-
- let selected = self.selected.clone();
- let entries = marked.iter().map(|(idx, v)| {
+ .map(|selected| selected)
+ .or(Some(marked.len().saturating_sub(1)));
+ let selected = self.selected;
+ let entries = marked.values().enumerate().map(|(idx, v)| {
  let modifier = match selected {
- Some(selected) if *idx == selected => Modifier::BOLD,
+ Some(selected) if idx == selected => Modifier::BOLD,
  _ => Modifier::empty(),
  };
  let name = Text::Styled(