Instead of trying to make http://, https://, and ftp:// URLs
indicative of some sort of pattern of transport helper usage, make
them a special case which runs the "curl" helper, and leave the
mechanism by which arbitrary helpers will be chosen entirely to future
work.
Signed-off-by: Daniel Barkalow <barkalow@iabervon.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>