Added temporary responsive design

app/assets/stylesheets/pages/projects.scss

@@ -744,8 +744,13 @@ pre.light-well {
     width: 300px;
   }
 
-  > .input-group > .compare-dropdown-toggle {
-    width: 200px;
+  &.from .compare-dropdown-toggle {
+    width: 237px;
+  }
+
+  &.to .compare-dropdown-toggle {
+    width: 254px;
+  }
 
   .dropdown-toggle-text {
     display: block;
@@ -755,6 +760,44 @@ pre.light-well {
     white-space: nowrap;
     width: 100%;
   }
+}
+
+.compare-ellipsis {
+  display: inline;
+}
+
+@media (max-width: $screen-xs-max) {
+  .compare-form-group {
+    .input-group {
+      width: 100%;
+
+      & > .compare-dropdown-toggle {
+        width: 100%;
+      }
+    }
+
+    .dropdown-menu {
+      width: 100%;
+    }
+  }
+
+  .compare-switch-container {
+    text-align: center;
+    padding: 0 0 $gl-padding;
+
+    .commits-compare-switch {
+      float: none;
+    }
+  }
+
+  .compare-ellipsis {
+    display: block;
+    text-align: center;
+    padding: 0 0 $gl-padding;
+  }
+
+  .commits-compare-btn {
+    width: 100%;
   }
 }
 

app/views/projects/compare/_form.html.haml

 = form_tag namespace_project_compare_index_path(@project.namespace, @project), method: :post, class: 'form-inline js-requires-input' do
   .clearfix
     - if params[:to] && params[:from]
+      .compare-switch-container
         = link_to icon('exchange'), {from: params[:to], to: params[:from]}, {class: 'commits-compare-switch has-tooltip', title: 'Switch base of comparison'}
-    .form-group.dropdown.compare-form-group.js-compare-from-dropdown
+    .form-group.dropdown.compare-form-group.from.js-compare-from-dropdown
       .input-group.inline-input-group
         %span.input-group-addon from
         = hidden_field_tag :from, params[:from]
         = button_tag type: 'button', class: "form-control compare-dropdown-toggle js-compare-dropdown", required: true, data: { refs_url: refs_namespace_project_path(@project.namespace, @project), toggle: "dropdown", target: ".js-compare-from-dropdown", selected: params[:from], field_name: :from } do
           .dropdown-toggle-text= params[:from] || 'Select branch/tag'
       = render "ref_dropdown"
-    = "..."
-    .form-group.dropdown.compare-form-group.js-compare-to-dropdown
+    .compare-ellipsis ...
+    .form-group.dropdown.compare-form-group.to.js-compare-to-dropdown
       .input-group.inline-input-group
         %span.input-group-addon to
         = hidden_field_tag :to, params[:to]