fixes merge request edit bug where it would generate a cloned file and not remove the previous one

Gemfile.lock

@@ -432,7 +432,6 @@ GEM
     mail_room (0.8.0)
     method_source (0.8.2)
     mime-types (2.99.2)
-    mime-types-data (3.2016.0521)
     mimemagic (0.3.1)
     mini_portile2 (2.1.0)
     minitest (5.7.0)

app/controllers/projects/blob_controller.rb

@@ -38,6 +38,11 @@ class Projects::BlobController < Projects::ApplicationController
   end
 
   def update
+    unless params[:file_name].empty?
+      @previous_path = @path
+      @path = params[:file_name]
+    end
+
     after_edit_path =
       if from_merge_request && @target_branch == @ref
         diffs_namespace_project_merge_request_path(from_merge_request.target_project.namespace, from_merge_request.target_project, from_merge_request) +