Updated libgit2

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Add GetGitLastErr(CString, int)

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Can use libgit2 to revert commit

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>