Option to skip existing files with restore action and --force

[Christopher Foo]

I decided to restore to another external hdd and left it overnight. I checked this morning and I got hit by bug LP#862485 and bug LP#749876. Attempting to restore again will give the usual

 Restore destination directory [blahblah] already exists.
 Will not overwrite.

so I tried using the --force argument as well. Unfortunatly, that means it has to do restore everything again..

So, it would be nice if there was an option that proceeds with restoring into an existing directory but skips existing files in the destination.

Duplicity version: rev 831 from duplicity-0.6-series + hax patch from LP#662442
Python version: Python 2.7.2+
OS Distro and version: ubuntu 11.10
Type of target filesystem: ntfs
Command: PYTHONPATH=. bin/duplicity restore file:///media/CHFOO2/backups/backups-laptop /media/HP\ SimpleSave/chris/restore/ --verbosity info --force

(I tried looking at the source code to see if I can write up a quick hax but it looks like theres too many deltrees() in the logic.. )