Add a git-peek-remote command that talks with upload-pack the
same way git-fetch-pack and git-clone-pack do, to show the
references the remote side has on the standard output.

A later patch introduces git-ls-remote that implements a UI to
store tag values retrieved using this command.
Signed-off-by: NJunio C Hamano <junkio@cox.net>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>