Comment 4 for bug 619478

In the context of the discussion on this patch:
https://code.edge.launchpad.net/~parthm/bzr/173274-export-hooks/+merge/35919

I am going to un-duplicate this bug so that we can create a patch for a 'bzr export --all' or 'bzr export --uncommitted' against this and have further discussion here if needed.
Johns point about --uncommitted having a different meaning from the 'merge --uncommitted' usage seems valid to me, so perhaps we can use --all as the option here? I will start on a patch with --all, we can review the option name either here or when the patch is up for review.