[Dirvish] Expire removes most recent backup?

[Barton C Massey]

It looks like dirvish-expire has no qualms about removing
the most recent image in a vault.  This seems to me to be a
bad idea.  

Since dirvish-expire is run before the actual backups,
there's a period when there may be no recent backup on the
disk---that seems to me like an unecessary and scary
vulnerability, especially given the propensity of a good
backing-up to expose flaws in the underlying filesystems and
whatnot.  The expire won't normally save much space anyway,
since presumably the next incremental will put most of it
back anyhow.

I considered whether to just run dirvish-expire after the
backup period, but that leads to potential for the other
kind of scary scenario, especially if dirvish-expire is
happy to remove the latest image.

Any chance someone could fix this so that dirvish-expire
will leave the most recent bits alone, at least as an
option?

    Bart Massey
    bart at cs.pdx.edu