Handle situations where the previous patch release is a direct ancestor of HEAD

[aaruni96]

Fixes #13

[lgoettgens]

I am not sure if this is possible to do with an option. In the past, we also had periods in AA/Nemo where we used release branches.
Could you instead traverse the git tree and verify that the intermediate patch releases are ancestors of the current master?
And what about scenarios where we have a first patch release on the master branch, then do a minor bump on master but later release more patch releases on a release branch?

[aaruni96]

Thanks for the hint @lgoettgens . Can you check that the new solution makes more sense?

[lgoettgens]

I don't understand all the details of the script, but this seems reasonable to me. (Just the PR title needs a tweak.)