views: add series navigation buttons for patch-detail view

patchwork/templates/patchwork/submission.html

@@ -20,6 +20,20 @@
   <h1>{{ submission.name }}</h1>
 </div>
 
+<div class="btn-group pull-right">
+  <a class="btn btn-default {% if not next_submission %} disabled {% endif %}"
+  {% if next_submission %} href="{% url 'patch-detail' project_id=project.linkname msgid=next_submission.encoded_msgid %}" {% endif %}>
+    next
+  </a>
+</div>
+
+<div class="btn-group pull-right">
+  <a class="btn btn-default {% if not previous_submission %} disabled {% endif %}"
+    {% if previous_submission %} href="{% url 'patch-detail' project_id=project.linkname msgid=previous_submission.encoded_msgid %}" {% endif %}>
+    previous
+  </a>
+</div>
+
 <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

@@ -133,6 +133,20 @@ def patch_detail(request, project_id, msgid):
     if errors:
         context['errors'] = errors
 
+    try:
+        context['previous_submission'] = Patch.objects.get(
+            series=patch.series, number=patch.number - 1
+        )
+    except Patch.DoesNotExist:
+        context['previous_submission'] = None
+
+    try:
+        context['next_submission'] = Patch.objects.get(
+            series=patch.series, number=patch.number + 1
+        )
+    except Patch.DoesNotExist:
+        context['next_submission'] = None
+
     return render(request, 'patchwork/submission.html', context)