Our Composer vendor cache is keyed on the composer.lock file, which means every time a dependency changes, the cache gets thrown away and Composer downloads every package from scratch. With Renovate opening merge requests all day, that's a lot of downloading. To speed things up, I wanted to add a second cache for Composer's download cache to our shared GitLab CI config - but no matter what I did, one of the caches kept vanishing. It took me far longer than I'd like to admit to work out why - extends doesn't merge lists. THE SETUP GitLab lets a job...