fetch, pull, and push didn't know their options. They do now. merge's
options are factored into a variable so they can be shared between
_git_merge and _git_pull
Signed-off-by: Jay Soffian <jaysoffian@gmail.com> Acked-by: Shawn O. Pearce <spearce@spearce.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>