linux sha256sum?

[NicolasConstant]

NicolasConstant/sengi#441

[NicolasConstant]

Some insights on why those checksum aren't applied on all packages currently:

• They are generated automatically by electron-builder
• It seems they only generate them for builds that supports electron's builder auto-update capability

If we want checksum for every packages, we have to implement it ourselves.

Looking to @sid-the-sloth insights, Mdview seems to have an interesting way of doing it, their build trigger a script after all artifacts are done, and it's inside this script that the magic occurs.

I don't really know if the integration of this script would be flawless or would need some modification to work with sengi's build.

If you have some time on your hands, feel free to fork the project and check that, it you can get it working I'll be happy to merge your PR.