Allow empty foldernames

Empty foldernames (as they could be created through nametrans) were
failing as the uidvalidity and status files names as determined by
folder/Base.py:getfolderbasename() lead to invalid file names ''.

Fix this by handling empty file names and translating them to '.' which
leads to the special file name 'dot'. (this special value existed before
and was not invented by this patch)

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

offlineimap/folder/Base.py

@@ -72,11 +72,15 @@ class BaseFolder(object):
             return self.getname()
 
     def getfolderbasename(self):
-        foldername = self.getname()
-        foldername = foldername.replace(self.repository.getsep(), '.')
-        foldername = re.sub('/\.$', '/dot', foldername)
-        foldername = re.sub('^\.$', 'dot', foldername)
-        return foldername
+        """Return base file name of file to store Status/UID info in"""
+        if not self.name:
+            basename = '.'
+        else: #avoid directory hierarchies and file names such as '/'
+            basename = self.name.replace('/', '.')
+        # replace with literal 'dot' if final path name is '.' as '.' is
+        # an invalid file name.
+        basename = re.sub('(^|\/)\.$','\\1dot', basename)
+        return basename
 
     def isuidvalidityok(self):
         """Does the cached UID match the real UID

offlineimap/folder/LocalStatus.py

@@ -28,7 +28,7 @@ class LocalStatusFolder(BaseFolder):
         self.root = root
         self.sep = '.'
         self.config = config
-        self.filename = repository.getfolderfilename(name)
+        self.filename = os.path.join(root, self.getfolderbasename())
         self.messagelist = {}
         self.repository = repository
         self.savelock = threading.Lock()

offlineimap/folder/LocalStatusSQLite.py

@@ -115,7 +115,7 @@ class LocalStatusSQLiteFolder(LocalStatusFolder):
             plaintextfilename = os.path.join(
                 self.repository.account.getaccountmeta(),
                 'LocalStatus',
-                re.sub('(^|\/)\.$','\\1dot', self.name))
+                self.getfolderbasename(self.name))
             # MIGRATE from plaintext if needed
             if os.path.exists(plaintextfilename):
                 self.ui._msg('Migrating LocalStatus cache from plain text '