Add core.objstore_uses_plumbing setting

Implement the idea suggested by Peff on the git mailing list. When
copying objects from offspring repositories into objstore, don't rely on
git porclelain commands, but use direct file copy and git plumbing to
achive the same result, but with a lot fewer cycles spent.

Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
3 files changed