Don't show "Add README" link in an empty repository if user doesn't have access to push

Closes #3094

CHANGELOG

@@ -16,6 +16,7 @@ v 8.1.0 (unreleased)
   - Show notifications button when user is member of group rather than project (Grzegorz Bizon)
   - Fix bug preventing mentioned issued from being closed when MR is merged using fast-forward merge.
   - Fix nonatomic database update potentially causing project star counts to go negative (Stan Hu)
+  - Don't show "Add README" link in an empty repository if user doesn't have access to push (Stan Hu)
   - Fix error preventing displaying of commit data for a directory with a leading dot (Stan Hu)
   - Speed up load times of issue detail pages by roughly 1.5x
   - If a merge request is to close an issue, show this on the issue page (Zeger-Jan van de Weg)

app/views/projects/empty.html.haml

@@ -8,15 +8,18 @@
 .gray-content-block.center
   %h3.page-title
     The repository for this project is empty
+  - if can?(current_user, :download_code, @project)
     %p
       If you already have files you can push them using command line instructions below.
       %br
+      - if can?(current_user, :push_code, @project)
         Otherwise you can start with
         = link_to "adding README", new_readme_path, class: 'underlined-link'
         file to this project.
 
-.prepend-top-20
-.empty_wrapper
+- if can?(current_user, :download_code, @project)
+  .prepend-top-20
+  .empty_wrapper
     %h3.page-title-empty
       Command line instructions
     %div.git-empty