doc: Show banner for prereleases

docs/_static/custom.css

@@ -30,6 +30,13 @@
     /*margin: -4px -4px 0 0;*/
 }
 
+#dev-warning {
+    background: #ffe;
+    border: 1px solid #aaa;
+    padding: 10px;
+    margin-bottom: 1em;
+}
+
 div.body h1,
 div.body h2,
 div.body h3,

docs/_templates/sidebar-top.html

@@ -1,6 +1,14 @@
 <link href='http://fonts.googleapis.com/css?family=Amethysta:400' rel='stylesheet'>
 <script async defer src="https://buttons.github.io/buttons.js"></script>
 
+{% if prerelease %}
+<script>
+$(document).ready(function() {
+    $('div.body').prepend('<div id="dev-warning">Warning: This is the documentation for the development version of Falcon.</div>')
+});
+</script>
+{% endif %}
+
 <div id="logo">
     <div id="logo-text"><a href="{{ pathto(master_doc) }}">Falcon</a></div>
     <a href="{{ pathto(master_doc) }}"><img src="{{ pathto('_static/img/logo.png', 1) }}" width="163" height="211" alt="Falcon Web Framework Logo"/></a>

docs/conf.py

@@ -77,6 +77,10 @@ cfg = configparser.SafeConfigParser()
 cfg.read('../setup.cfg')
 tag = cfg.get('egg_info', 'tag_build')
 
+html_context = {
+  'prerelease': bool(tag),  # True if tag is not the empty string
+}
+
 # The short X.Y version.
 version = '.'.join(falcon.__version__.split('.')[0:2]) + tag