While we configure the LeiStore git repos and DBs to have a
restrictive umask, lei may also write to Maildirs/mboxes/etc.
We will follow mutt behavior when saving files/messages to the FS.
We only want to create files which are only readable by the local
user since this is intended for private mail and could be used
on shared systems.
We may allow passing the umask on a per-command-basis, but it's
probably not worth the effort to support.