This Plushu build hook plugin builds an App Container using progrium/buildstep.
The monolithic container approach used by buildstep isn't particularly elegant, and in its build process, buildstep itself misses the mark in a few ways. For a more modular, Plushu-friendly build system, one should use plushu-build-cedarish, while using the plushu-buildpacks plugin to manage buildpacks, using a meta-plugin like plushu-heroku-buildpacks to get a default set of plugins.