Resolve "Project homepage > Plus dropdown on mobile screens"

app/assets/stylesheets/framework/tables.scss

 .table-holder {
   margin: 0;
+  overflow: auto;
 }
 table {

app/views/projects/tree/_tree_header.html.haml

@@ -6,7 +6,7 @@
     = render 'shared/ref_switcher', destination: 'tree', path: @path, show_create: true
     - if on_top_of_branch?
-      - addtotree_toggle_attributes = { href: '#', 'data-toggle': 'dropdown', 'data-target': '.add-to-tree-dropdown' }
+      - addtotree_toggle_attributes = { href: '#', 'data-toggle': 'dropdown', 'data-target': '.add-to-tree-dropdown', 'data-boundary': 'window' }
     - else
       - addtotree_toggle_attributes = { title: _("You can only add files when you are on a branch"), data: { container: 'body' }, class: 'disabled has-tooltip' }