Add support for XDG Base Directory Specification

$XDG_CONFIG_HOME/offlineimap/config will now be tried before
the canonical ~/.offlineimaprc.

Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>

Changelog.rst

@@ -16,6 +16,10 @@ OfflineIMAP v6.5.6 (YYYY-MM-DD)
   adds mechanics to change message labels (Abdó Roig-Maranges)
 * Allow to migrate status data across differend backends
   (Abdó Roig-Maranges)
+* Support XDG Base Directory Specification
+  (if $XDG_CONFIG_HOME/offlineimap/config exists, use it as the
+  default configuration path; ~/.offlineimaprc is still tried after
+  XDG location) (GitHub#32)
 
 
 OfflineIMAP v6.5.5 (2013-10-07)

README.md

@@ -74,6 +74,13 @@ to do is specify a directory for your folders to be in (on the localfolders
 line), the host name of your IMAP server (on the remotehost line), and your
 login name on the remote (on the remoteuser line).  That's it!
 
+If you prefer to be XDG-compatible,
+  http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html
+then substitute the above ``~/.offlineimaprc'' with
+``$XDG\_CONFIG\_HOME/offlineimap/config'' and don't forget to set
+XDG\_CONFIG\_HOME properly if you want it to be different from
+the default ``$HOME/.config'' for any reason.
+
 To run OfflineIMAP, you just have to say `offlineimap` ― it will fire
 up, ask you for a login password if necessary, synchronize your folders,
 and exit.  See?

docs/MANUAL.rst

@@ -63,6 +63,9 @@ set, and you can read about other features later with `offlineimap.conf`.
 
 Check out the `Use Cases`_ section for some example configurations.
 
+If you want to be XDG-compatible, you can put your configuration file into
+`$XDG_CONFIG_HOME/offlineimap/config`.
+
 
 OPTIONS
 =======

docs/doc-src/FAQ.rst

@@ -77,6 +77,15 @@ based in instructions submitted by Chris Walker::
     That URL also has more details on making OfflineIMAP work with Windows.
 
 
+Does OfflineIMAP supports XDG Base Directory specification?
+-----------------------------------------------------------
+
+Yes.  We are trying to use `$XDG_CONFIG_HOME/offlineimap/config`
+as the primary configuration file, falling back to `~/.offlineimaprc`
+if configuration file location was not explicitely specified at the
+command line.
+
+
 Does OfflineIMAP support mbox, mh, or anything else other than Maildir?
 -----------------------------------------------------------------------
 

offlineimap/init.py

@@ -101,9 +101,8 @@ class OfflineImap:
               "or to sync some accounts that you normally prefer not to.")
 
         parser.add_option("-c", dest="configfile", metavar="FILE",
-                  default="~/.offlineimaprc",
-                  help="Specifies a configuration file to use in lieu of "
-                       "%default.")
+                  default=None,
+                  help="Specifies a configuration file to use")
 
         parser.add_option("-d", dest="debugtype", metavar="type1,[type2...]",
                   help="Enables debugging for OfflineIMAP. This is useful "
@@ -165,7 +164,19 @@ class OfflineImap:
         globals.set_options (options)
 
         #read in configuration file
-        configfilename = os.path.expanduser(options.configfile)
+        if not options.configfile:
+            # Try XDG location, then fall back to ~/.offlineimaprc
+            xdg_var = 'XDG_CONFIG_HOME'
+            if not xdg_var in os.environ or not os.environ[xdg_var]:
+                xdg_home = os.path.expanduser('~/.config')
+            else:
+                xdg_home = os.environ[xdg_var]
+            options.configfile = os.path.join(xdg_home, "offlineimap", "config")
+            if not os.path.exists(options.configfile):
+                options.configfile = os.path.expanduser('~/.offlineimaprc')
+            configfilename = options.configfile
+        else:
+            configfilename = os.path.expanduser(options.configfile)
 
         config = CustomConfigParser()
         if not os.path.exists(configfilename):