Author here. Yes, I am also the one that loves to see alternatives on topic of interest to me on HN. However putting an effort to publish different take on something already 'solved' is either because I want my own solution no matter what (I don't) or because other solutions didn't fully cover all my use cases (they didn't). I would gladly use somebody else code instead of my own, if that was possible.
Two scripts linked at the bottom of README.md are almost perfect and I used one or another for years, but one of them sometimes misses to hard link with previous backup, creating new full backup and wasting resources -- not something that's easy to detect since they all look correct before 'du' or similar analysis.
saf solves few of the problems I faced during the years in a elegant way: multiple targets, target related commands, reliability. Why not XY? Why not saf?