git init: optionally allow a directory argument

git init: optionally allow a directory argument

When starting a new repository, I see my students often say

    % git init newrepo

and curse git.  They could say

    % mkdir newrepo; cd newrepo; git init

but allowing it as an obvious short-cut may be nicer.

Signed-off-by: Nanako Shiraishi <nanako3@lavabit.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>