MakefilePackage looks like it provides a lot of clean-up from the way things previously were. Unfortunately, it both uses advanced features and is completely undocumented (see https://github.com/LLNL/spack/search?utf8=%E2%9C%93&q=MakefilePackage ). The result is I have a really hard time knowing how the code in this PR works.

I would like to see documentation on MakefilePackage submitted (in a separate PR) before this PR is merged.

@alalazo: when you get a chance, do you mind documenting the build systems? I could help with this as well but I think they're used frequently enough now it would be good to have docs soon-ish.

when you get a chance, do you mind documenting the build systems?

@tgamblin Sure. I am currently finishing the porting to pytest of all the tests that require mocking (hopefully I will be done by the end of the week). Then I'll start working on build system docs.