We currently point the HEAD of a newly cloned repo to the
same ref as the parent repo's HEAD. While a user can then
"git checkout -b foo origin/foo" whichever branch they
choose, it is more convenient and more efficient to tell
clone which branch you want in the first place.
Based on a patch by Kirill A. Korinskiy.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>