Improve tagging behavior when package content does not change

[tobalsan]

This avoids pushing "empty" tags to split repositories when their content did not change. This mimics the Symfony monorepo behavior, as it applies only to patch versions, e.g. 2.3.1. For minor and major versions, new tags are still pushed to split repositories, whether they contain changes or not.

In effect, here's the behavior to expect for a split package inside a monorepo:

• when you push to the monorepo a new tag
  • and the target package has bee updated
    • the new tag is pushed
  • the target package has no change, and the tag is a patch version (e.g. 2.3.1)
    • nothing happens (the tag is skipped in the split repository)
  • the target package has no change, and the tag is a minor or major version (e.g. 2.4 or 3.0)
    → the new tag is pushed to the split repository