--diff should show packages that were installed/upgrade

[assapir]

As in the title, currently --diff doesn't have any efect.

[gotmax23]

It looks like --diff support was added in #36. Can you please give instructions to reproduce the bug? Does it still occur if you run your playbook with --diff --check?

[assapir]

From looking on #36 and on the current code, it seems like this diff doesn't apply in case of an upgrade, just when installing a package.