What is the default refspec for fetch?

Hi,

In a repo where no remote.<name>.fetch config parameter is set what should a "git fetch" do? My experiments let me think it's "HEAD:FETCH_HEAD". Right?

I came to this question after finding out that when I clone repos in bare mode then they don't have and explicit remote.<name>.fetch in their config. But a "git fetch" sometimes updated "something".

Ciao
  Chris