Use XDG Base Directory specification log path

Also discourage from using a hidden log file in $HOME for hacking

CHANGELOG

@@ -1,5 +1,7 @@
 qtile x.x.x, released xxxx-xx-xx:
     * file path changes (XDG Base Directory specification)
+        - the default log file path changed from ~/.qtile.log to
+          ~/.local/share/qtile/qtile.log
         - the cache directory changed from ~/.cache to ~/.cache/qtile
     * features
         - wlan widget shows when you are disconnected and uses a configurable

CONTRIBUTING.md

@@ -19,9 +19,10 @@ has two qualities:
    Do not combine multiple problems even they seem to be similar. Write
    different reports for each problem.
 
-To give more information about your bug you can append logs from `~/.qtile.log`
-or on occasionally events you can capture bugs with `xtrace` for this have a deeper 
-look on the documentation about [capturing an xtrace](http://qtile.readthedocs.org/en/latest/manual/hacking.html#capturing-an-xtrace)
+To give more information about your bug you can append logs from
+`~/.local/share/qtile/qtile.log` or on occasionally events you can capture bugs
+with `xtrace` for this have a deeper look on the documentation about
+[capturing an xtrace](http://qtile.readthedocs.org/en/latest/manual/hacking.html#capturing-an-xtrace)
 
 Writing code
 ============

docs/manual/hacking.rst

@@ -89,7 +89,7 @@ Qtile's conversations with the X server. To capture one of these, create an
 
 .. code-block:: bash
 
-  exec xtrace qtile >> ~/.qtile.log
+  exec xtrace qtile >> ~/qtile.log
 
 This will put the xtrace output in Qtile's logfile as well. You can then
 demonstrate the bug, and paste the contents of this file into the bug report.

libqtile/log_utils.py

@@ -66,7 +66,7 @@ def format(self, record):
         return message + self.reset_seq
 
 
-def init_log(log_level=WARNING, log_path='~/.%s.log', log_truncate=False,
+def init_log(log_level=WARNING, log_path=True, log_truncate=False,
              log_size=10000000, log_numbackups=1, log_color=True):
     formatter = Formatter(
         "%(asctime)s %(levelname)s %(name)s %(filename)s:%(funcName)s():L%(lineno)d %(message)s"
@@ -85,6 +85,15 @@ def init_log(log_level=WARNING, log_path='~/.%s.log', log_truncate=False,
 
     # If we have a log path, we'll also setup a log file
     if log_path:
+        if not isinstance(log_path, str):
+            data_directory = os.path.expandvars('$XDG_DATA_HOME')
+            if data_directory == '$XDG_DATA_HOME':
+                # if variable wasn't set
+                data_directory = os.path.expanduser("~/.local/share")
+            data_directory = os.path.join(data_directory, 'qtile')
+            if not os.path.exists(data_directory):
+                os.makedirs(data_directory)
+            log_path = os.path.join(data_directory, '%s.log')
         try:
             log_path %= 'qtile'
         except TypeError:  # Happens if log_path doesn't contain formatters.