Set maxsplit=0 for :spawn and split manually.

Fixes #759.

CHANGELOG.asciidoc

@@ -56,6 +56,7 @@ Changed
 - The `ui -> user-stylesheet` setting now also takes file paths relative to the config directory.
 - The `content -> cookies-accept` setting now has new `no-3rdparty` (default) and `no-unknown-3rdparty` values to block third-party cookies. The `default` value got renamed to `all`.
 - Improved startup time by reading the webpage history while qutebrowser is open.
+- The way `:spawn` splits its commandline has been changed slightly to allow commands with flags.
 
 Deprecated
 ~~~~~~~~~~

doc/help/commands.asciidoc

@@ -529,20 +529,24 @@ Preset the statusbar to some text.
 
 [[spawn]]
 === spawn
-Syntax: +:spawn [*--userscript*] [*--verbose*] [*--detach*] 'args' ['args' ...]+
+Syntax: +:spawn [*--userscript*] [*--verbose*] [*--detach*] 'cmdline'+
 
 Spawn a command in a shell.
 
 Note the {url} variable which gets replaced by the current URL might be useful here.
 
 ==== positional arguments
-* +'args'+: The commandline to execute.
+* +'cmdline'+: The commandline to execute.
 
 ==== optional arguments
 * +*-u*+, +*--userscript*+: Run the command as an userscript.
 * +*-v*+, +*--verbose*+: Show notifications when the command started/exited.
 * +*-d*+, +*--detach*+: Whether the command should be detached from qutebrowser.
 
+==== note
+* This command does not split arguments after the last argument and handles quotes literally.
+* With this command, +;;+ is interpreted literally instead of splitting off a second command.
+
 [[stop]]
 === stop
 Stop loading in the current/[count]th tab.

qutebrowser/browser/commands.py

@@ -21,6 +21,7 @@
 
 import re
 import os
+import shlex
 import posixpath
 import functools
 import xml.etree.ElementTree
@@ -919,8 +920,9 @@ class CommandDispatcher:
         finally:
             self._tabbed_browser.setUpdatesEnabled(True)
 
-    @cmdutils.register(instance='command-dispatcher', scope='window')
-    def spawn(self, userscript=False, verbose=False, detach=False, *args):
+    @cmdutils.register(instance='command-dispatcher', scope='window',
+                       maxsplit=0)
+    def spawn(self, cmdline, userscript=False, verbose=False, detach=False):
         """Spawn a command in a shell.
 
         Note the {url} variable which gets replaced by the current URL might be
@@ -930,11 +932,15 @@ class CommandDispatcher:
             userscript: Run the command as an userscript.
             verbose: Show notifications when the command started/exited.
             detach: Whether the command should be detached from qutebrowser.
-            *args: The commandline to execute.
+            cmdline: The commandline to execute.
         """
-        log.procs.debug("Executing: {}, userscript={}".format(
-            args, userscript))
-        cmd, *args = args
+        try:
+            cmd, *args = shlex.split(cmdline)
+        except ValueError as e:
+            raise cmdexc.CommandError("Error while splitting command: "
+                                      "{}".format(e))
+        log.procs.debug("Executing {} with args {}, userscript={}".format(
+            cmd, args, userscript))
         if userscript:
             self.run_userscript(cmd, *args, verbose=verbose)
         else: