Test `stack sdist` or equivalent on CI
Clarification and motivation
We want all our packages to be potentially uploadable to Hackage, for that we need stack sdist
to work. Sometimes it doesn't work, so we want CI to prevent its breakages.
Running stack sdist
on CI is complicated.
Acceptance criteria
CI fails whenever stack sdist
fails. It does not have to run literally stack sdst
, so we can add "with high probability".