How to detect recipe updates of particular packages in the upstream

[akirak]

When a recipe is updated in the upstream MELPA repository, it is likely that the corresponding package source requires updating. melpa/melpa#9344 is an example of such a case. It would be nice if there were a way to detect changes in the relevant package recipes. A simple solution would be to update everything: all registries and all package sources. However, that is not what I want to do, because the whole point of twist is to update individual packages separately.