Previously, since we created a new copy of ~/dev prior to every backup
run, we caused new ctimes to be set every time which lead to many
changed files on every backup run.
This change removes the deletion of ~/dev-backup after backups and
ensures deleted files get removed from ~/dev-backup as well.
This change should also drastically reduce download bandwidth during prunes.
Generating a list of paths for restic to backup introduces some issues:
- restic matches incremental backups by paths, changing paths cause new
backups
- logs and a lot of restic commands print all the paths, which makes it
basically unusable
Thus I've reverted to using static `paths` and excluding patterns via
the `--exclude-file` argument.
To reduce files to backup from `~/dev`, a preStart job was added to the
systemd service: It clones the directory via `rsync` with `.gitignore`
files being respected.