When a package is updated, it is possible that the package update causes an issue for future package upgrades. A sensible way to test this is to manually bump the PR and attempt installing the updated package. This is not too difficult for just one package, but doing so for every package installed on an image is not easy. It would be helpful to have a Bitbake task for bumping the PR on the PR server. There are two use cases that I think would be useful. The first is: bitbake -c bump_pr <recipe> which then only bumps the PR on the packages generated by the listed recipe. The second is: bitbake -c bump_pr <image> which then bumps the PR on all packages which are installed on <image>. This would then make full system upgrades easier to test.
I'm not convinced this needs to be done in bitbake itself, it should be relatively simple to write a script that uses tinfoil to do the PR increments outside of bitbake.
We don't feel this API would make sense. You can cause all packages to rebuild (and hence bump PR) by changing common code like the package_rpm class, even by just adding whitespace. There are therefore other ways you would do this and the API as stated doesn't make sense. If we were to do something it would make sense through tinfoil API as Ross mentions.