Cache: Interaction with bors

[MikailBag]

It seems that bors-ng + actions/cache = problems.

Problem

Bors-ng is a merge bot. When pull request is approved, it merges PR head into special staging branch and waits for CI status. If build is green, bors fast-forwards master up to staging. It means that there will be no workflow execution for master branch, because commit is already 'used' (when it was on staging). So, no caches for master will be created (They will be created on staging, but such objects are invisible to other branched).

I will be very glad if I am mistaken and in fact caching works just fine with bors.
Otherwise, I'd like to listen for some advice.

[joshmgross]

Hey @MikailBag, you're correct that a cache created for staging won't be accessible by PRs (which only read caches from the PR merge branch and the default branch/master).

It means that there will be no workflow execution for master branch, because commit is already 'used`

If you have a push trigger in your workflow for changes to master, I would hope that you would still get a build on master after that fast-forward

I haven't used any merge bots, but if you want caching for new PR builds, you need a build on your default branch.

[MikailBag]

Thanks for clarification.
It turns out that caching works fine!