Use wsgi.url_scheme instead of ad-hoc CGI checks.

Instead of each place in hgweb_mod that needs to check for SSL or get
the protocol scheme (http vs. https) doing it ad-hoc, make them just
look at the wsgi.url_scheme which because of previous patches is now
always set correctly.

mercurial/hgweb/hgweb_mod.py

@@ -787,7 +787,8 b' class hgweb(object):'
             style = req.form['style'][0]
         mapfile = style_map(self.templatepath, style)
 
-        if req.env.get('HTTPS'):
+        proto = req.env.get('wsgi.url_scheme')
+        if proto == 'https':
             proto = 'https'
             default_port = "443"
         else:
@@ -1070,7 +1071,7 b' class hgweb(object):'
         # replayed
         ssl_req = self.configbool('web', 'push_ssl', True)
         if ssl_req:
-            if not req.env.get('HTTPS'):
+            if req.env.get('wsgi.url_scheme') != 'https':
                 bail(_('ssl required\n'))
                 return
             proto = 'https'