Add focus_tab command

TODO

@@ -48,7 +48,6 @@ somehow unfocus elements (hide blinking cursor) when insert mode is left?
 tabs: some more padding?
 exec command for shell
 custom stylesheet
-Alt+N to focus tab N
 Really fix URL detection properly
 
 hints

qutebrowser/config/configdata.py

@@ -505,6 +505,15 @@ DATA = OrderedDict([
         ('<Ctrl-B>', 'scroll_page 0 -1'),
         ('<Ctrl-D>', 'scroll_page 0 0.5'),
         ('<Ctrl-U>', 'scroll_page 0 -0.5'),
+        ('<Alt-1>', 'focus_tab 1'),
+        ('<Alt-2>', 'focus_tab 2'),
+        ('<Alt-3>', 'focus_tab 3'),
+        ('<Alt-4>', 'focus_tab 4'),
+        ('<Alt-5>', 'focus_tab 5'),
+        ('<Alt-6>', 'focus_tab 6'),
+        ('<Alt-7>', 'focus_tab 7'),
+        ('<Alt-8>', 'focus_tab 8'),
+        ('<Alt-9>', 'focus_tab 9'),
         ('<Backspace>', 'back'),
         ('<Left>', '${h}'),
         ('<Down>', '${j}'),

qutebrowser/widgets/_tabbedbrowser.py

@@ -322,6 +322,23 @@ class TabbedBrowser(TabWidget):
         """
         self.paste(sel, True)
 
+    @cmdutils.register(instance='mainwindow.tabs')
+    def focus_tab(self, arg=None, count=None):
+        if ((arg is None and count is None) or
+                (arg is not None and count is not None)):
+            message.error("Either argument or count must be given!")
+            return
+        try:
+            idx = int(arg) if arg is not None else count
+        except ValueError:
+            message.error("Invalid argument: {}".format(arg))
+            return
+        if 1 <= idx <= self.count():
+            self.setCurrentIndex(idx - 1)
+        else:
+            message.error("Index out of bounds!")
+            return
+
     @pyqtSlot(str, str)
     def on_config_changed(self, section, option):
         """Update tab config when config was changed."""