Clean up after the shell runner

We have several jobs using the shell executor (I would probably try to make those run with the docker executor - which we already use for other jobs - if I were to do it over, but there is no time for that right now). They work fine, but it leaves a checkout of the project in $token/<N>/<user or group>/<project>. Some of our projects are quite huge, so we really don’t want to spend disc on multiple copies.

It seems as if there is no problem in just deleting those, but are there any good ways to keep some around, so the caching effect (I guess that’s why they are kept) isn’t completely lost?