Add new expansion key for mbnames.peritem config variable

It is called localfolders and holds expanded name for the same
variable for the local repository of the account that is being
processed.

GitHub issue: https://github.com/OfflineIMAP/offlineimap/issues/21
Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>

offlineimap/mbnames.py

@@ -21,6 +21,7 @@ import re                               # for folderfilter
 from threading import Lock
 
 boxes = {}
+localroots = {}
 config = None
 accounts = None
 mblock = Lock()
@@ -30,9 +31,10 @@ def init(conf, accts):
     config = conf
     accounts = accts
 
-def add(accountname, foldername):
+def add(accountname, foldername, localfolders):
     if not accountname in boxes:
         boxes[accountname] = []
+        localroots[accountname] = localfolders
     if not foldername in boxes[accountname]:
         boxes[accountname].append(foldername)
 
@@ -64,10 +66,12 @@ def genmbnames():
                                          {'re': re})
         itemlist = []
         for accountname in boxes.keys():
+            localroot = localroots[accountname]
             for foldername in boxes[accountname]:
                 if folderfilter(accountname, foldername):
                     itemlist.append({'accountname': accountname,
-                                     'foldername': foldername})
+                                     'foldername': foldername,
+                                     'localfolders': localroot})
         itemlist.sort(key = mb_sort_keyfunc)
         format_string = config.get("mbnames", "peritem", raw=1)
         itemlist = [format_string % d for d in itemlist]