I would be interested in something like this:
command: [ --smallfiles ]
This is possible with docker and docker compose like described here: https://blog.sneawo.com/blog/2017/01/26/fast-tests-with-in-memory-mongodb/
I will answer myself with a workaround I made:
We merged a patch 2 weeks ago that includes support for tmpfs, for trusted repositories. It is included in 0.8-rc.5. Reference pull request https://github.com/cncd/pipeline/pull/22
Nice work, looks like 0.8 will be a great release.