upload-pack: support define shallow boundary by excluding revisions

upload-pack: support define shallow boundary by excluding revisions

This should allow the user to say "create a shallow clone of this branch
after version <some-tag>".

Short refs are accepted and expanded at the server side with expand_ref()
because we cannot expand (unknown) refs from the client side.

Like deepen-since, deepen-not cannot be used with deepen. But deepen-not
can be mixed with deepen-since. The result is exactly how you do the
command "git rev-list --since=... --not ref".

Signed-off-by: Nguyễn Thái Ngọc Duy <redacted>
Signed-off-by: Junio C Hamano <redacted>