Use XDG Base Directory specification path for prompt widget's history…

… file

CHANGELOG

@@ -3,6 +3,8 @@ qtile x.x.x, released xxxx-xx-xx:
         - the default log file path changed from ~/.qtile.log to
           ~/.local/share/qtile/qtile.log
         - the cache directory changed from ~/.cache to ~/.cache/qtile
+        - the prompt widget's history file changed from ~/.qtile_history to
+          ~/.cache/qtile/prompt_history
     * features
         - wlan widget shows when you are disconnected and uses a configurable
           format

libqtile/widget/prompt.py

@@ -362,7 +362,8 @@ def __init__(self, name="prompt", **config):
             self.original_background = self.background
         # If history record is on, get saved history or create history record
         if self.record_history:
-            self.history_path = os.path.expanduser('~/.qtile_history')
+            self.history_path = os.path.join(utils.get_cache_dir(),
+                                             'prompt_history')
             if os.path.exists(self.history_path):
                 with open(self.history_path, 'rb') as f:
                     try: