Fix blog by year index.

Add an additional context data that is always the entire list of years,
and use that instead of date_list for the current queryset.

www/conservancy/apps/blog/urls.py

@@ -61,6 +61,9 @@ def all_authors():
     return sorted(Person.objects.filter(entry__isnull=False).distinct(),
                   key=last_name)
 
+def all_year_list():
+    return Entry.objects.dates(date_field, 'year')
+
 # The functions are passed to the context uncalled so they will be
 # called for each web request.  If we want to only make these database
 # queries a single time when a web server process begins, call both
@@ -68,3 +71,4 @@ def all_authors():
 
 extra_context['all_authors'] = all_authors
 extra_context['all_tags'] = all_tags_by_use_amount
+extra_context['all_year_list'] = all_year_list

www/conservancy/templates/base_blog.html

@@ -24,10 +24,10 @@
 (<a href="/feeds/blog/?tag={{ tag.slug }}">rss</a>)</li>
 {% endfor %}
 </ul>
-{% if date_list %}
+{% if all_year_list %}
 <h2>Blog Index by Year</h2>
 <ul>
-{% for year in date_list reversed %}<li><a href="{{ year|date:"Y" }}/">{{ year|date:"Y" }}</a></li>{% endfor %}
+{% for year in all_year_list reversed %}<li><a href="{{ year|date:"Y" }}/">{{ year|date:"Y" }}</a></li>{% endfor %}
 </ul>
 {% endif %}