message: use make_mut for cleaner code
diff: @@ -68,9 +68,7 @@ impl Context {
  &*link
  );
  }
  - let mut inner: Vec<_> = (**prev).clone();
  - inner.push(summary.clone());
  - *prev = Rc::new(inner);
  + Rc::make_mut(prev).push(summary.clone());
  return Ok(false);
  }
  debug!("checking if {} is already activated", summary.package_id());
  @@ -246,15 +244,13 @@ impl Context {
  if !reqs.used.is_empty() {
  let pkgid = s.package_id();
  - let set = self.resolve_features
  + let set = Rc::make_mut(self.resolve_features
  .entry(pkgid.clone())
  - .or_insert_with(|| Rc::new(HashSet::new()));
  + .or_insert_with(|| Rc::new(HashSet::new())));
  - let mut inner: HashSet<_> = (**set).clone();
  for feature in reqs.used {
  - inner.insert(InternedString::new(feature));
  + set.insert(InternedString::new(feature));
  }
  - *set = Rc::new(inner);
  }
  Ok(ret)
  