Workaround for n+1 in Projects::TreeController#show

See https://gitlab.com/gitlab-org/gitlab-ce/issues/38261

app/controllers/projects/tree_controller.rb

@@ -35,7 +35,10 @@ class Projects::TreeController < Projects::ApplicationController
       end
 
       format.json do
-        render json: TreeSerializer.new(project: @project, repository: @repository, ref: @ref).represent(@tree)
+        # n+1: https://gitlab.com/gitlab-org/gitlab-ce/issues/38261
+        Gitlab::GitalyClient.allow_n_plus_1_calls do
+          render json: TreeSerializer.new(project: @project, repository: @repository, ref: @ref).represent(@tree)
+        end
       end
     end
   end