Allow subject counts to increase from zero.

Before this fix, you could expand a stream, and then any
subjects that already had a zero count could not be
incremented when new messages came in, until you rebuilt
the subject list again.

(imported from commit 98c95e201f6ec745d7c857da6f42495c8bf88ee0)

zephyr/static/js/stream_list.js

@@ -131,6 +131,7 @@ exports.set_subject_count = function (stream, subject, count) {
         return;
     }
 
+    count_span.removeClass("zero_count");
     update_count_in_dom(count_span, value_span, count);
 };
 
@@ -150,7 +151,7 @@ function rebuild_recent_subjects(stream, subject) {
     $.each(subjects, function (idx, subject_obj) {
         var num_unread = unread.num_unread_for_subject(stream, subject_obj.canon_subject);
         subject_obj.unread = num_unread;
-        subject_obj.has_unread = num_unread !== 0;
+        subject_obj.is_zero = num_unread === 0;
 
         if (subject === subject_obj.canon_subject) {
             active_orig_subject = subject_obj.subject;
@@ -161,6 +162,7 @@ function rebuild_recent_subjects(stream, subject) {
     stream_li.append(templates.render('sidebar_subject_list',
                                       {subjects: subjects,
                                        stream: stream}));
+
     if (active_orig_subject !== undefined) {
         get_subject_filter_li(stream, active_orig_subject).addClass('active-subject-filter');
     }

zephyr/static/styles/zephyr.css

@@ -1600,3 +1600,7 @@ li.expanded_subject {
 #pin_info_question:hover {
     cursor:  pointer;
 }
+
+.zero_count {
+    display: none;
+}

zephyr/static/templates/sidebar_subject_list.handlebars

@@ -3,9 +3,9 @@
     <li class='expanded_subject' data-name='{{subject}}'>
         <a href='#narrow/stream/{{../stream}}/subject/{{subject}}'>
           {{subject}}
-          {{#if has_unread}}
-            <span class="subject_count">(<span class="value">{{unread}}</span>)</span>
-          {{/if}}
+          <span class="subject_count {{#if is_zero}}zero_count{{/if}}">
+              (<span class="value">{{unread}}</span>)
+          </span>
         </a>
     </li>
     {{/each}}