Add next button to navigate within a patch series

patchwork/templates/patchwork/submission.html

@@ -20,6 +20,15 @@
   <h1>{{ submission.name }}</h1>
 </div>
 
+{% if next_submission %}
+<div class="btn-group pull-right">
+  <a class="btn btn-default"
+      href="{% url 'patch-detail' project_id=project.linkname msgid=next_submission.encoded_msgid %}">
+    next
+  </a>
+</div>
+{% endif %}
+
 <table id="patch-meta" class="patch-meta" data-submission-type={{submission|verbose_name_plural|lower}} data-submission-id={{submission.id}}>
   <tr>
     <th>Message ID</th>

patchwork/views/patch.py

@@ -136,6 +136,13 @@ def patch_detail(request, project_id, msgid):
         related_same_project = []
         related_different_project = []
 
+    context['next_submission'] = None
+    patch_series = patch.series.patches.all()
+    num_patches = patch.series.patches.count()
+    for idx in range(num_patches - 1):
+        if patch.id == patch_series[idx].id:
+            context['next_submission'] = patch_series[idx + 1]
+
     context['comments'] = comments
     context['checks'] = Patch.filter_unique_checks(
         patch.check_set.all().select_related('user'),