Create LocalStatus or LocalStatusSQLite folders

Depending on the configuration we use the plain text or the new
experimental sqlite backend for the LocalStatus cache. Make plain text
the default status backend but allow people to configure
status_backend=sqlite in their [Account ...] section.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/repository/LocalStatus.py

@@ -18,7 +18,8 @@
 
 from Base import BaseRepository
 from offlineimap import folder
-import offlineimap.folder.LocalStatus
+from offlineimap.folder.LocalStatus import LocalStatusFolder
+from offlineimap.folder.LocalStatusSQLite import LocalStatusSQLiteFolder
 import os
 import re
 
@@ -26,9 +27,25 @@ class LocalStatusRepository(BaseRepository):
     def __init__(self, reposname, account):
         BaseRepository.__init__(self, reposname, account)
         self.directory = os.path.join(account.getaccountmeta(), 'LocalStatus')
+
+        #statusbackend can be 'plain' or 'sqlite'
+        backend = self.account.getconf('status_backend', 'plain')
+        if backend == 'sqlite':
+            self._backend = 'sqlite'
+            self.LocalStatusFolderClass = LocalStatusSQLiteFolder
+            self.directory += '-sqlite'
+        elif backend == 'plain':
+            self._backend = 'plain'
+            self.LocalStatusFolderClass = LocalStatusFolder
+        else:
+            raise SyntaxWarning("Unknown status_backend '%s' for account '%s'" \
+                                % (backend, account.name))
+
         if not os.path.exists(self.directory):
             os.mkdir(self.directory, 0700)
-        self.folders = None
+
+        # self._folders is a list of LocalStatusFolders()
+        self._folders = None
 
     def getsep(self):
         return '.'
@@ -40,16 +57,22 @@ class LocalStatusRepository(BaseRepository):
         return os.path.join(self.directory, foldername)
 
     def makefolder(self, foldername):
-        # "touch" the file, truncating it.
+        """Create a LocalStatus Folder
+
+        Empty Folder for plain backend. NoOp for sqlite backend as those
+        are created on demand."""
+        # Invalidate the cache.
+        self._folders = None
+        if self._backend == 'sqlite':
+            return
+
         filename = self.getfolderfilename(foldername)
         file = open(filename + ".tmp", "wt")
         file.write(offlineimap.folder.LocalStatus.magicline + '\n')
-        file.flush()
-        os.fsync(file.fileno())
         file.close()
         os.rename(filename + ".tmp", filename)
         # Invalidate the cache.
-        self.folders = None
+        self._folders = None
 
     def getfolder(self, foldername):
         """Return the Folder() object for a foldername"""
@@ -72,4 +95,3 @@ class LocalStatusRepository(BaseRepository):
         """Forgets the cached list of folders, if any.  Useful to run
         after a sync run."""
         self._folders = None
-