Say you have the following parts: parts: main: plugin: nil dependent: plugin: nil after: [main] `main` always needs to be staged before `dependent` is even pulled, which means if `main` ends up cleaning or re-running the stage step, `dependent`'s pull step is now dirty. Today this logic happens when cleaning the stage step of `main`: the snapcraft CLI knows `dependent` depends upon it, and actually loads up the pull state for `dependent`, modifies it saying that a dependency has changed, and then saves it. Then the next time `dependent` runs, it sees that its pull state is dirty. This works, to an extent, but quickly gets complicated once more reasons for needing to rebuild are introduced (e.g. detecting local source changes). It's also error-prone: if an error occurs when saving `dependent`s state, then it doesn't consider itself out of date even though a dependency change took place. Rather than manually handling dependency changes, the snapcraft CLI should actually check to see if dependencies have updated (or _should_ update) for a given part.