Whenever we rebuild a CI docker image, cloning operations/puppet or mediawiki/core from scratch is a pain. We should use a local cache as a reference.
Self note: Tyler and Antoine did something similar with Quibble using a local cache which is them exposed as a volume to clone from
Can be done by:
This way the clone is mostly a local copy.
We cant use --reference, since later /srv/git is not availble.
docker build doesn't support mounting a volume.
For CI the git cache is on the host which is then mounted at run time with -v /srv/git:/srv/git:ro. zuul-cloner uses that to clone the repo.