Add an --override-restore argument.

See #523.

doc/qutebrowser.1.asciidoc

@@ -46,6 +46,9 @@ It was inspired by other browsers/addons like dwb and Vimperator/Pentadactyl.
 *-r* 'SESSION', *--restore* 'SESSION'::
     Restore a named session.
 
+*-R*, *--override-restore*::
+    Don't restore a session even if one would be restored.
+
 === debug arguments
 *-l* 'LOGLEVEL', *--loglevel* 'LOGLEVEL'::
     Set loglevel

qutebrowser/app.py

@@ -261,6 +261,7 @@ class Application(QApplication):
                 message.error('current', "set: {} - {}".format(
                     e.__class__.__name__, e))
 
+        if not self._args.override_restore:
             self._load_session(self._args.session)
         session_manager = objreg.get('session-manager')
         if not session_manager.did_load:

qutebrowser/qutebrowser.py

@@ -55,6 +55,9 @@ def get_argparser():
                         metavar=('SECTION', 'OPTION', 'VALUE'))
     parser.add_argument('-r', '--restore', help="Restore a named session.",
                         dest='session')
+    parser.add_argument('-R', '--override-restore', help="Don't restore a "
+                        "session even if one would be restored.",
+                        action='store_true')
 
     debug = parser.add_argument_group('debug arguments')
     debug.add_argument('-l', '--loglevel', dest='loglevel',