git-fetch: Allow fetching the remote HEAD

git-fetch: Allow fetching the remote HEAD

... with:

$ git fetch ${remote} HEAD

Also

$ git fetch ${remote} :${localref}

worked, but

$ git fetch ${remote} HEAD:{localref}

didn't. Now both are equivalent.

Signed-off-by: Santi Béjar <sbejar@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>