GUI support for viewing new/changed files in backup

[mullermn]

Currently Backrest provides plenty of information on how much backing up it's been doing, but I don't believe there's any easy way to see which files specifically were processed during a backup, only the overall snapshot. I'm setting up a new set of backups to a cloud service and tuning what is/isn't included to keep volumes down while making sure the important stuff is protected, and it'd be really handy to see which files were modified and added (& removed?) in a given backup.

The UI could be modified to support this fairly easily by adding a tickbox selector to the snapshot browser to choose between viewing the complete snapshot or just changes since the previous, with the tree trimmed to the relevant subset if it's selected.

Stretch goal:
At the cost of more UI work it might also be nice to be able to compare any two points in time to each other, rather than just any given snapshot to its predecessor.

[DominikBritz]

+1