http2: mark experimental and developer options

mercurial/httpconnection.py

@@ -126,6 +126,7 b' class http2handler(urllib2.HTTPHandler, '
         self.ui = ui
         self.pwmgr = pwmgr
         self._connections = {}
+        # developer config: ui.http2debuglevel
         loglevel = ui.config('ui', 'http2debuglevel', default=None)
         if loglevel and not _configuredlogging:
             _configuredlogging = True

mercurial/url.py

@@ -469,6 +469,7 b' def opener(ui, authinfo=None):'
     construct an opener suitable for urllib2
     authinfo will be added to the password manager
     '''
+    # experimental config: ui.usehttp2
     if ui.configbool('ui', 'usehttp2', False):
         handlers = [httpconnectionmod.http2handler(ui, passwordmgr(ui))]
     else: