Identify and fix messages with FMD5 inconsistencies

Introduce the '--migrate-fmd5-using-nametrans' option which migrates the
FMD5 hashes from versions prior to 6.3.5.

It seems that commit 'Apply nametrans to all Foldertypes' (6b2ec956cf)
introduced a regression because it changed the FMD5 part of the filename
calculated by OfflineIMAP. Thus, OfflineIMAP believes that the messages
has been removed and adds them back.

For more information, see:
http://www.offlineimap.org/configuration/2016/02/12/debian-upgrade-from-jessie-to-stretch.html

Bug-Debian: https://bugs.debian.org/812108
Reported-by: François <francois@avalenn.eu>
Signed-off-by: Ilias Tsitsimpis <i.tsitsimpis@gmail.com>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>

offlineimap/init.py

@@ -25,11 +25,12 @@ import logging
 from optparse import OptionParser
 
 import offlineimap
-from offlineimap import accounts, threadutil, syncmaster
+from offlineimap import accounts, threadutil, syncmaster, folder
 from offlineimap import globals
 from offlineimap.ui import UI_LIST, setglobalui, getglobalui
 from offlineimap.CustomConfig import CustomConfigParser
 from offlineimap.utils import stacktrace
+from offlineimap.repository import Repository
 
 import traceback
 import collections
@@ -50,6 +51,8 @@ class OfflineImap:
         options, args = self.__parse_cmd_options()
         if options.diagnostics:
             self.__serverdiagnostics(options)
+        elif options.migrate_fmd5:
+            self.__migratefmd5(options)
         else:
             return self.__sync(options)
 
@@ -120,6 +123,10 @@ class OfflineImap:
                   help="specifies an alternative user interface"
                   " (quiet, basic, syslog, ttyui, blinkenlights, machineui)")
 
+        parser.add_option("--migrate-fmd5-using-nametrans",
+                  action="store_true", dest="migrate_fmd5", default=False,
+                  help="migrate FMD5 hashes from versions prior to 6.3.5")
+
         (options, args) = parser.parse_args()
         globals.set_options (options)
 
@@ -427,3 +434,21 @@ class OfflineImap:
         for account in allaccounts:
             if account.name not in activeaccounts: continue
             account.serverdiagnostics()
+
+    def __migratefmd5(self, options):
+        activeaccounts = self.config.get("general", "accounts")
+        if options.accounts:
+            activeaccounts = options.accounts
+        activeaccounts = activeaccounts.replace(" ", "")
+        activeaccounts = activeaccounts.split(",")
+        allaccounts = accounts.AccountListGenerator(self.config)
+
+        for account in allaccounts:
+            if account.name not in activeaccounts:
+                continue
+            localrepo = Repository(account, 'local')
+            if localrepo.getfoldertype() != folder.Maildir.MaildirFolder:
+                continue
+            folders = localrepo.getfolders()
+            for f in folders:
+                f.migratefmd5(options.dryrun)