concurrent synchronization of nnmaildir directories

[James Leifer <James.Leifer@inria.fr>]

Hi,

I'm switching some of my groups from the trusty-rusty nnmh to the more
robust nnmaildir 8-).  My main motivation is to be able to easily
synchronize maildirs on my desktop and laptop.  I'll do the sync with
unison or some scripts I cook up myself.

To do the synchronization, I have to be able to add, modify, and
delete already delivered messages.  In particular, is it safe to do
the following operations while nnmaildir is *running*?

* Add a new message with its marks, i.e. add a file in foo/cur and
  update foo/.nnmaildir/{marks/{read,reply,...},nov} appropriately.

* Modify the marks of an existing message, i.e. add and delete entries
  in foo/.nnmaildir/marks/{read,reply,...}

* Delete an existing message, i.e. delete a file in foo/cur and the
  corresponding entries in foo/.nnmaildir/{marks/{read,reply,...},nov}.

Since the filesystem doesn't allow me to add a message and its marks
in a single atomic step, does the order of the operations and the
modification times of the files matter?

Is it dangerous to do these operations while nnmaildir is regenerating
nov data, reading or saving marks, etc?

Do I need to do anything to foo/.nnmaildir/num?

Comments would be gratefully received.

-James