I see some patches referring to this message but I don't understand what it
Warning: Remote HEAD refers to nonexistent ref, unable to checkout.
Would someone please explain the message? Is my repository complete?
When you clone from a repository, git clone does a default checkout using
the branch referred to by HEAD. If HEAD does not exist on the remote repo,
git clone simply does not checkout any branch (but your local repo is ok).
At least that's what I understood from reading git-clone.sh.
You can see all the remote branches with
git branch -a
and checkout a new local branch on top of them with
git checkout -b local_branch remote_branch