Although they’re not in the tutorials I linked, I’ve done what’s in the one you did (added the ssh key, …)

I’ve also created the empty repository the following way:

git init

While being in the testing directory, then I did:

git add .

And then a simple commit of an empty file, the comes the error.

Thanks for the answer

In order for the server side repository to accept a push, it needs to be created with --bare flag.

In order to initially set up any Git server, you have to export an existing repository into a new bare repository — a repository that doesn’t contain a working directory. This is generally straightforward to do. In order to clone your repository to create a new bare repository, you run the clone command with the --bare option. By convention, bare repository directories end in .git

See here.

Thanks again, well now there is no error. But the output isn’t the same, while in the tutorial shows this:

user@host ~/git/testing $ git push origin master
Counting objects: 4, done.
Delta compression using up to 2 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), 266 bytes, done.
Total 3 (delta 1), reused 1 (delta 0)
To ssh://git@git.domain.tld/repository.git
   0e78fdf..e6a8ddc  master -> master

in my case is just:

everything up-to-date

NOTE: I’m doing inside my-project.git

git init && git remote add origin git@git.droplet.com:my-project.git

I’ve solved it, Thanks!! It was a misunderstanding between server side and client side.