For pull-requests coming from forks, we don't have access to the secrets. This is currently failing CI for all PRs from forks as docker cannot write the cache after running the tests.
Pull-Request: #4604.
The `unreachable_pub` lint makes us aware of uses of `pub` that are not actually reachable from the crate root. This is considered good because it means reading a `pub` somewhere means it is actually public API. Some of our crates are quite large and keeping their entire API surface in your head is difficult.
We should strive for most items being `pub(crate)`. This lint helps us enforce that.
Pull-Request: #3735.
