Add config to limit size of undo stack

qutebrowser/config/configdata.yml

@@ -1764,6 +1764,14 @@ tabs.pinned.frozen:
     default: True
     desc: Force pinned tabs to stay at fixed URL.
 
+tabs.undo_stack_size:
+  default: 100
+  type:
+    name: Int
+    minval: -1
+    maxval: maxint
+  desc: Number of close tab actions to remember, per window (-1 for no maximum).
+
 tabs.wrap:
   default: true
   type: Bool

qutebrowser/mainwindow/tabbedbrowser.py

@@ -19,6 +19,7 @@
 
 """The main tabbed browser widget."""
 
+import collections
 import functools
 
 import attr
@@ -131,7 +132,9 @@ def __init__(self, *, win_id, private, parent=None):
         else:
             self.cur_load_started.connect(self._leave_modes_on_load)
 
-        self._undo_stack = []
+        # This init is never used, it is immediately thrown away in the next line.
+        self._undo_stack = collections.deque()
+        self._update_stack_size()
         self._filter = signalfilter.SignalFilter(win_id, self)
         self._now_focused = None
         self.search_text = None
@@ -142,6 +145,13 @@ def __init__(self, *, win_id, private, parent=None):
         self.is_private = private
         config.instance.changed.connect(self._on_config_changed)
 
+    def _update_stack_size(self):
+        newsize = config.instance.get('tabs.undo_stack_size')
+        if newsize < 0:
+            newsize = None
+        # We can't resize a collections.deque so just recreate it >:(
+        self._undo_stack = collections.deque(self._undo_stack, maxlen=newsize)
+
     def __repr__(self):
         return utils.get_repr(self, count=self.widget.count())
 
@@ -151,6 +161,8 @@ def _on_config_changed(self, option):
             self._update_favicons()
         elif option == 'window.title_format':
             self._update_window_title()
+        elif option == 'tabs.undo_stack_size':
+            self._update_stack_size()
         elif option in ['tabs.title.format', 'tabs.title.format_pinned']:
             self.widget.update_tab_titles()