Update for libgit2 api changes.
Update for libgit2 api changes.

lekkas/livegrep,wfxiang08/livegrep,wfxiang08/livegrep,paulproteus/livegrep,lekkas/livegrep,lekkas/livegrep,paulproteus/livegrep,wfxiang08/livegrep,paulproteus/livegrep,wfxiang08/livegrep,lekkas/livegrep,lekkas/livegrep,paulproteus/livegrep,paulproteus/livegrep,paulproteus/livegrep,wfxiang08/livegrep,lekkas/livegrep,wfxiang08/livegrep