If you have something to ask you can add the question here! This is a wiki after all :) Also, if you have an answer to an unanswered question feel free to write here. Oh, and before you can edit, you must login.

What is Git and how to use it?

Git is a version control system. This means that you can save snapshots of your
project. You can see what has changed between the snapshots and go back in history.

For more help with Git and how to use it with YouSource, see Git_Help or Tutorial. For further reading, checkout the online book Pro Git.

I got “warning: remote HEAD refers to nonexistent ref, unable to checkout.” when I cloned a repository

No worries, this just means that in the local repository there is no branch selected.
When you make a commit, branch named ‘master’ will be created.

How do I generate and upload the required SSH key?

See the SSH_key_help page.

Why do I need to upload my public SSH key?

When you push to a Git repository, your public key is how we authenticate
you and check if you have the permission to do a commit to a given repository.

How did my avatar/mugshot end up on this site? I'm not even registered!

We use Gravatar.com for user avatars. If you
haven’t registered on YouSource, someone else may have pushed commits with your
name and/or email in them which we in turn hash and send to Gravatar.com to
find an avatar image. If you want it changed you should either register and
upload an avatar of your own, or go to Gravatar.com and change it.

What exactly do the “Mirroring” and “Mirror url” options mean in repository settings? Can YouSource mirror from GitLab?