message: Use HashSet for xml package deduplication
  `Vec::dedup` only removes consecutive elements, but HashSet implicitly
  dedups regardless of order.
diff: /// </packages>
  /// </coverage>
  /// ```
  +use std::collections::HashSet;
  use std::error;
  use std::fmt;
  use std::fs::File;
  @@ -308,14 +309,12 @@ struct Package {
  }
  fn render_packages(config: &Config, traces: &TraceMap) -> Vec<Package> {
  - let mut dirs: Vec<&Path> = traces
  + let dirs: HashSet<&Path> = traces
  .files()
  .into_iter()
  .filter_map(|x| x.parent())
  .collect();
  - dirs.dedup();
  -
  dirs.into_iter()
  .map(|x| render_package(config, traces, x))
  .collect()
  