For my particular usecase of duplicity for backupsit's not the matter of space efficiency, but the matter of consistency of mtimes. I have a lot of small backup archives with few files from file system in each. And every backup archive stores its own mtimes for system directories (/root, /home/user, /usr/local/bin, /etc, ...) Every time I wish to restore archive system directories get new mtime. Another inconvinience of this workflow is when I run duplicity verify I see a lot of dirs with changed mtimes, while I'm only interested in added/changed/deleted files.
> 3. that said, if you need it _and_ implement it properly and provide a patch, why not
Yes, it sounds fair, I'll try to implement this.