Add :debug-log-capacity command

qutebrowser/misc/utilcmds.py

@@ -234,3 +234,16 @@ def repeat_command(win_id, count=None):
     cmd = runners.last_command[mode_manager.mode]
     commandrunner = runners.CommandRunner(win_id)
     commandrunner.run(cmd[0], count if count is not None else cmd[1])
+
+
+@cmdutils.register(debug=True, name='debug-log-capacity')
+def log_capacity(capacity: int):
+    """Change the number of log lines to be stored in RAM.
+
+    Args:
+       capacity: Number of lines for the log.
+    """
+    if capacity < 0:
+        raise cmdexc.CommandError("Can't set a negative log capacity!")
+    else:
+        log.ram_handler.change_log_capacity(capacity)

qutebrowser/utils/log.py

@@ -511,6 +511,9 @@ class RAMHandler(logging.Handler):
                 lines.append(fmt(record))
         return '\n'.join(lines)
 
+    def change_log_capacity(self, capacity):
+        self._data = collections.deque(self._data, maxlen=capacity)
+
 
 class ColoredFormatter(logging.Formatter):