Clearing the cache

Description

GitLab Runners use cache to speed up execution by reusing existing data. But sometimes it leads to inconsistent behaviors, and actually there is no way to force starting with a fresh copy of the cache.

We should implement a way to do that, so weird cases are easily solved using the UI.

Proposal

Add a button in CI/CD > Pipelines to clean up the cache. This works by increasing a counter in the database, and using the value of that counter to create the key for the cache. After a push, a new key is generated and the old cache is not valid anymore, and eventually garbage collector will remove it.

Design