Someone abused the credentials in your .git/config file

[DanielRuf]

A person going by the name gitsbackup has overwritten your commits.
You can easily recover them by pushing from the cloned repository which was used for this attack. Make sure to delete the credentials in the .git/config file then and change your password.

Use git push -u origin master -f && git push --tags -f from your local clone to push all references for master, tags and so on to the remote and then enable 2FA in your account.

See my full answer at https://security.stackexchange.com/a/209473/6090