Before I made a commit in my dotfiles repo I saw something weird that appeared in my
clean = git hawser clean %f
smudge = git hawser smudge %f
required = true
Since life is too short to read all the wild stuff that randomly appears in my config files, I just added that modification to my commit. After some days, people started asking on my dotfiles repo where did those things appeared.
In a happy ending, somebody talked to Github's support and those lines are added by Github for Mac.
But I still don't know what