<% @taxons = @taxon && @taxon.parent ? @taxon.parent.children : Spree::Taxon.roots %>
<%= form_tag spree.products_path, method: :get, class: "form-inline d-flex" do %>
  <div class="form-group">
    <% cache [I18n.locale, @taxons] do %>
      <%= select_tag :taxon,
            options_for_select([[Spree.t(:all_departments), '']] +
                                  @taxons.map {|t| [t.name, t.id]},
                                  @taxon ? @taxon.id : params[:taxon]), 'aria-label' => 'Taxon', class: "form-control mr-2" %>
    <% end %>
  </div>
  <div class="form-group">
    <%= search_field_tag :keywords, params[:keywords], placeholder: Spree.t(:search), class: "form-control mr-2" %>
  </div>
  <%= submit_tag Spree.t(:search), name: nil, class: "btn btn-success" %>
<% end %>

<% @taxons = @taxon && @taxon.parent ? @taxon.parent.children : Spree::Taxon.roots %>
<%= form_tag spree.products_path, method: :get, class: "ml-2 form-inline d-flex" do %>
  <div class="form-group">
    <% cache [I18n.locale, @taxons] do %>
      <%= select_tag :taxon,
            options_for_select([[Spree.t(:all_departments), '']] +
                                  @taxons.map {|t| [t.name, t.id]},
                                  @taxon ? @taxon.id : params[:taxon]), 'aria-label' => 'Taxon', class: "form-control mr-2" %>
    <% end %>
  </div>
  <div class="form-group">
    <%= search_field_tag :keywords, params[:keywords], placeholder: Spree.t(:search), class: "form-control mr-2" %>
  </div>
  <%= submit_tag Spree.t(:search), name: nil, class: "btn btn-success" %>
<% end %>

Add padding to search form
Add padding to search form
