worktree: sort the tree object.  Fixes #881
worktree: sort the tree object.  Fixes #881

Signed-off-by: Mark Bartel <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@spottybenny.ca>

mcuadros/go-git,go-git/go-git,go-git/go-git,src-d/go-git,mcuadros/go-git,src-d/go-git