refactored the `default_path` function in `sheets`.

And added two functions to `utils`:

* `get_userdata_dir`

  returns the default user data directory

* `get_default_data_dir`

  returns the default directory used for user data

Now which directory is used to store the user sheets,
is determined the following way:

1. If the `DEFAULT_CHEAT_DIR` environment variable is set, use it.

2. If a `.cheat` directory exists in the home directory, use it.

3. Use a `cheat` directory in the systems default directory for user data.

cheat/sheets.py

@@ -10,16 +10,16 @@ cheats = {}
 
 
 def default_path():
-    """ Returns the default cheatsheet path """
+    """ Returns the full path to the default cheatsheet directory """
 
     # the default path becomes confused when cheat is run as root, so fail
     # under those circumstances. (There is no good reason to need to run cheat
     # as root.)
     if os.name != 'nt' and os.geteuid() == 0:
-        die('Please do not run this application as root.');
+        die('Please do not run this application as root.')
 
     # determine the default cheatsheet dir
-    default_sheets_dir = os.environ.get('DEFAULT_CHEAT_DIR') or os.path.join(os.path.expanduser('~'), '.cheat')
+    default_sheets_dir = get_default_data_dir()
 
     # create the DEFAULT_CHEAT_DIR if it does not exist
     if not os.path.isdir(default_sheets_dir):

cheat/utils.py

@@ -1,6 +1,8 @@
 import os
 import sys
 
+from xdg.BaseDirectory import save_data_path
+
 
 def colorize(sheet_content):
     """ Colorizes cheatsheet content if so configured """
@@ -54,3 +56,35 @@ def prompt_yes_or_no(question):
 def warn(message):
     """ Prints a message to stderr """
     print >> sys.stderr, (message)
+
+
+def get_default_data_dir():
+    """
+    Returns the full path to the directory containing the users data.
+
+    Which directory is used, is determined the following way:
+
+    1. If the `DEFAULT_CHEAT_DIR` environment variable is set, use it.
+
+    2. If a `.cheat` directory exists in the home directory, use it.
+
+    3. Use a `cheat` directory in the systems default directory for user data.
+
+    """
+    user_dir = os.environ.get("DEFAULT_CHEAT_DIR")
+    if not user_dir:
+        user_dir = os.path.expanduser(os.path.join("~", ".cheat"))
+        if not os.path.exists(user_dir):
+            user_dir = get_userdata_dir()
+    return user_dir
+
+
+def get_userdata_dir():
+    """
+    Returns the full path to a `cheat` directory in the platform specific
+    default data directory for the current user.
+
+    .. note:: The directory is created, if it's not already present.
+
+    """
+    return save_data_path('cheat')

setup.py

@@ -24,5 +24,6 @@ setup(
     install_requires = [
         'docopt >= 0.6.1',
         'pygments >= 1.6.0',
+        'pyxdg  >= 0.25'
     ]
 )