Merge branch 'backport_from_ee' into 'master'

Fix of on-hover state for 'Edit' button on tree view

It's already reviewed and merged to EE, so it's just a back-port.

See merge request !4823

app/helpers/blob_helper.rb

@@ -29,7 +29,7 @@ module BlobHelper
     if !on_top_of_branch?(project, ref)
       button_tag "Edit", class: "btn disabled has-tooltip btn-file-option", title: "You can only edit files when you are on a branch", data: { container: 'body' }
     elsif can_edit_blob?(blob, project, ref)
-      link_to "Edit", edit_path, class: 'btn btn-file-option'
+      link_to "Edit", edit_path, class: 'btn btn-sm'
     elsif can?(current_user, :fork_project, project)
       continue_params = {
         to:     edit_path,