Since disk_free_limit == 0 is now the default, add some claruity and help text around that.

deps/rabbitmq_management/priv/www/js/help.js

@@ -175,6 +175,8 @@ HELP = {
         <dd>Rate at which basic.return is sent to publishers for undeliverable  messages published with the \'immediate\' flag set.</dd>\
       </dl>',
 
+    'disk-monitoring-no-watermark' : 'There is no disk space low watermark set. RabbitMQ will not take any action to avoid running out of disk space.',
+
     'foo': 'foo' // No comma.
 };
 

deps/rabbitmq_management/priv/www/js/tmpl/node.ejs

@@ -85,9 +85,13 @@
          <%= fmt_bytes(node.disk_free) %>
        </div>
    <% } %>
-   <sub><%= fmt_bytes(node.disk_free_limit) %> low watermark</sub>
+   <% if (node.disk_free_limit == 0) { %>
+     <sub>No low watermark <span class="help" id="disk-monitoring-no-watermark"></span></sub>
+   <% } else { %>
+     <sub><%= fmt_bytes(node.disk_free_limit) %> low watermark </sub>
+   <% } %>
 <% } else { %>
-         (not monitored)
+         (not available)
 <% } %>
       </td>
     </tr>

deps/rabbitmq_management/priv/www/js/tmpl/overview.ejs

@@ -166,9 +166,14 @@ if (version_warning) {
          <%= fmt_bytes(node.disk_free) %>
        </div>
    <% } %>
-   <sub><%= fmt_bytes(node.disk_free_limit) %> low watermark </sub>
+   <% if (node.disk_free_limit == 0) { %>
+     <sub>No low watermark <span class="help" id="disk-monitoring-no-watermark"></span></sub>
+   <% } else { %>
+     <sub><%= fmt_bytes(node.disk_free_limit) %> low watermark </sub>
+   <% } %>
+
 <% } else { %>
-         (not monitored)
+         (not available)
 <% } %>
      </td>
      <td class="r">