Remove old code in TreeHelper#flatten_tree

app/helpers/tree_helper.rb

@@ -136,18 +136,9 @@ module TreeHelper
   end
 
   # returns the relative path of the first subdir that doesn't have only one directory descendant
-  # rubocop: disable CodeReuse/ActiveRecord
   def flatten_tree(root_path, tree)
-    return tree.flat_path.sub(%r{\A#{Regexp.escape(root_path)}/}, '') if tree.flat_path.present?
-
-    subtree = Gitlab::Git::Tree.where(@repository, @commit.id, tree.path)
-    if subtree.count == 1 && subtree.first.dir?
-      return tree_join(tree.name, flatten_tree(root_path, subtree.first))
-    else
-      return tree.name
+    tree.flat_path.sub(%r{\A#{Regexp.escape(root_path)}/}, '')
   end
-  end
-  # rubocop: enable CodeReuse/ActiveRecord
 
   def selected_branch
     @branch_name || tree_edit_branch

lib/gitlab/git/rugged_impl/tree.rb

@@ -33,9 +33,11 @@ module Gitlab
               end
             end
 
-            # This is an optimization to reduce N+1 queries for Gitaly. It's
-            # currently done in TreeHelper#flatten_tree, but to emulate Gitaly
-            # as much as possible we populate the value here.
+            # This was an optimization to reduce N+1 queries for Gitaly
+            # (https://gitlab.com/gitlab-org/gitaly/issues/530).  It
+            # used to be done lazily in the view via
+            # TreeHelper#flatten_tree, so it's possible there's a
+            # performance impact by loading this eagerly.
             rugged_populate_flat_path(repository, sha, path, ordered_entries)
           end