[PATCH] Update git-core.spec.in

Update git-core spec file based on feedback from Fedora Extras review.

- update BuildRoot to be more specific
- eliminate Requires that must be satisfied for base system install
- drop Vendor
- use dist tag to differentiate between branches
- own %{_datadir}/git-core/
- use RPM_OPT_FLAGS in spec file

Signed-off-by: Chris Wright <chrisw@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>