[Feature request] CLI diff with saved versions of installed components to see real changes for new releases

[bennettdams]

Right now the diff command only compares a user's existing code with the "new" code from shadcn/ui.
As the library's concept allows and encourages to change the implementation of installed components, the given diff is often not useful, as it highly diverges from the new component code.

What I think would be nice:

When installing/updating components, their current version is saved in the component.json file.
Executing a diff then could be checked against specific versions: locally installed version vs. remote version.
That way a user can see the "real" changes and apply them to its own implementation if needed.