v0.8.7

This is a bugfix release to improve support for Borg 1.2.1. Changes in detail:

• Deal with new archive_progress key (#1353)
• Raise ValueError in case of unknown change type in diff json. By @real-yfprojects (#1350)
• Fix unlink action when repo combobox is empty. By @real-yfprojects (#1342)
• Show date of next backup. By @tal66 (#1319)