I have a few questions about controlling ASDF execution of compile/load operations:

1. Suppose I have performed successful `load-op` on a certain system. After some time and no changes to the source code of the system nor its dependencies, I run `load-system` again on the same system. How can I ensure that no compile/load action is performed?

2. Suppose I have a system `foo` that depends on `bar`. Now, I explicitly call `(load-system :bar)`. How can I ensure that when I call `(load-system :foo)` no compile/load action is performed on `bar`?

Sorry, maybe, these questions are trivial, but I couldn't find definite answers in the docs.