offlineimap smart backup synchronization = bidirectional synchronization without deleting any messages

[Edward Z. Yang]

Excerpts from proxym's message of Wed Dec 19 11:32:13 +0800 2012:
> Looks like I must to create own patch =)
> If I remove all from status folder I think it will be very very long
> synchronisation then.

Note that OfflineIMAP will very quickly figure out what messages already
exist on both ends (since the UIDs will match), so you will only pay for the delta.

Edward

> Looks like I must remove (from status folder) information about
> message which was deleted from remote repository...
> 
> 2012/12/19 Edward Z. Yang <ezyang at mit.edu>:
> > Excerpts from proxym's message of Tue Dec 18 22:57:24 +0800 2012:
> >> After I changed `no-delete-local` back to `no` ALL previously
> >> not-deleted messages (because of `no-delete-local yes`) are deleted
> >> from my local repository.
> >> This patch IS TOO DANGEROUS in case of no back synchronisation of
> >> messages to remote imap repository.
> >
> > Yes, what do you expect? OfflineIMAP sees that it's missing from the
> > remote and not from the local, and syncs accordingly.  The same applies
> > with maxage; if you unset it expect a lot of activity.
> >
> > One way to prevent OfflineIMAP from deleting anything is to remove
> > your status folder; then OfflineIMAP assumes everything is "unsynced"
> > and won't remove anything.
> >
> > Edward