Implement ui.makefolder and abort repo.makefolder() in dry-run mode

IMAP, Maildir, and LocalStatus abort if in dry-run mode. IMAP and Maildir
will log that they "would have" created a new folder.

This will probably fail later on as we can not cache messagelists on
folder that don't exist, so --dry-run is not yet safe when new folders
have been created.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

offlineimap/repository/Base.py

@@ -124,6 +124,7 @@ class BaseRepository(CustomConfig.ConfigHelperMixin, object):
         raise NotImplementedError
 
     def makefolder(self, foldername):
+        """Create a new folder"""
         raise NotImplementedError
 
     def deletefolder(self, foldername):

offlineimap/repository/IMAP.py

@@ -341,11 +341,11 @@ class IMAPRepository(BaseRepository):
             foldername = self.getreference() + self.getsep() + foldername
         if not foldername: # Create top level folder as folder separator
             foldername = self.getsep()
-
+        self.ui.makefolder(self, foldername)
+        if self.account.dryrun:
+            return
         imapobj = self.imapserver.acquireconnection()
         try:
-            self.ui._msg("Creating new IMAP folder '%s' on server %s" %\
-                              (foldername, self))
             result = imapobj.create(foldername)
             if result[0] != 'OK':
                 raise OfflineImapError("Folder '%s'[%s] could not be created. "

offlineimap/repository/LocalStatus.py

@@ -67,10 +67,11 @@ class LocalStatusRepository(BaseRepository):
 
         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
+            return # noop for sqlite which creates on-demand
+
+        if self.account.dryrun:
+            return # bail out in dry-run mode
 
         filename = self.getfolderfilename(foldername)
         file = open(filename + ".tmp", "wt")

offlineimap/repository/Maildir.py

@@ -81,7 +81,9 @@ class MaildirRepository(BaseRepository):
             levels will be created if they do not exist yet. 'cur',
             'tmp', and 'new' subfolders will be created in the maildir.
         """
-        self.debug("makefolder called with arg '%s'" % (foldername))
+        self.ui.makefolder(self, foldername)
+        if self.account.dryrun:
+            return
         full_path = os.path.abspath(os.path.join(self.root, foldername))
     
         # sanity tests

offlineimap/ui/UIBase.py

@@ -298,6 +298,12 @@ class UIBase(object):
                            (src_repo, dst_repo))
 
     ############################## Folder syncing
+    def makefolder(self, repo, foldername):
+        """Called when a folder is created"""
+        prefix = "[DRYRUN] " if self.dryrun else ""
+        self.info("{}Creating folder {}[{}]".format(
+                prefix, foldername, repo))
+
     def syncingfolder(self, srcrepos, srcfolder, destrepos, destfolder):
         """Called when a folder sync operation is started."""
         self.logger.info("Syncing %s: %s -> %s" % (srcfolder,