Set the base URL correctly to refer to '/' and not /app.html

The client app currently expects the base URL to refer to
the root URL for the Hypothesis web service and not the app.html
page for the sidebar. In particular, in the extension this
is used to determine where to make the '/app' call to get
a session token.

h/buildext.py

@@ -236,7 +236,7 @@ def build_chrome(args):
         with codecs.open(content_dir + '/app.html', 'w', 'utf-8') as fp:
             data = client_assets.render_app_html(
               api_url=api_url,
-              base_url=webassets_env.url + '/app.html',
+              base_url=args.base,
 
               # Google Analytics tracking is currently not enabled
               # for the extension

h/client_assets.py

@@ -64,6 +64,13 @@ def _app_html_context(webassets_env,
     else:
         ga_cookie_domain = 'auto'
 
+
+    # Angular requires that the <base> tag's href include
+    # a non-empty path component
+    if urlparse(base_url).path == '':
+        base_url += '/'
+
+
     return {
       'angular_templates': map(_angular_template_context,
                                ANGULAR_DIRECTIVE_TEMPLATES),
@@ -86,7 +93,8 @@ def render_app_html(webassets_env, base_url, api_url, websocket_url,
     Return the HTML for the Hypothesis app page,
     used by the sidebar, stream and single-annotation page.
 
-    :param base_url: The URL at which the page will be served
+    :param base_url: The base URL of the Hypothesis service
+                     (eg. https://hypothes.is/)
     :param api_url: The root URL for the Hypothesis service API
     :param websocket_url: The WebSocket URL which the client should connect to
     :param register_url: The URL which new users should be sent to in order to

h/views.py

@@ -36,7 +36,7 @@ def _handle_exc(request):
 def _render_app(request, extra={}):
     request.response.text = client_assets.render_app_html(
       api_url=request.route_url('api'),
-      base_url=request.url,
+      base_url=request.route_url('index'),
       extra=extra,
       ga_tracking_id=request.registry.settings.get('ga_tracking_id'),
       register_url=request.route_url('register'),