This patch renames the following documents and at the same time converts
them to the man format:
diffcore.txt -> gitdiffcore.txt (man section 7)
repository-layout.txt -> gitrepository-layout.txt (man section 5)
Other documents that reference the above ones are changed accordingly.
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>