expire related caches after changing HEAD

What does this MR do?

Ensures that, for example, the read me page of the project is updated when its HEAD changed via the settings page.

Are there points in the code the reviewer needs to double check?

Check if I missed other similar scenarios where similar problems exist.

Why was this MR needed?

Because all cache involving HEAD should be updated when HEAD changes.

What are the relevant issue numbers?

N/A.

Screenshots (if relevant)