CI: add reusable actions

[fufexan]

Describe your PR, what does it fix/add?

Allows reusing actions across the org, meaning less copied code and less chances of errors slipping in when a change is made.

• Nix: define strategy, which builds in parallel, faster than doing nix flake check (which does not guarantee the builds are run as the dependency graph dictates.)

Is there anything you want to mention? (unchecked code, possible bugs, found problems, breaking compatibility, etc.)

See my comment below.

Is it ready for merging, or does it need work?

I also want to create a conditional job:

• when wlroots gets updated, don't run Nix builds
• when there's no wlroots update, run the builds

The above conditional was replaced by simply running the wlroots update first, and re-cloning HEAD from the branch on the subsequent package build job.

[memchr]

FYI, there is a tool called act that lets you run and debug github actions locally, it's in nixpkgs I think.

[fufexan]

Damn, didn't know that. Thanks. However I think I've mostly finished this PR.

[fufexan]

Ok, so if there are both a pull_request and a push trigger, the wlroots update action will fail for one of them. Doesn't affect builds at all though. This should happen very rarely, only if vax decides to bump wlroots inside a PR. I think it's good enough for now.

Alternatively I could make it so that pull_request is never run if the PR ref is from this repo, but it's not worth the complication.

[memchr]

Maybe add a condition to skip this job in PR?

wlroots / wlroots ( nix-update-wlroots.yml )
Secret PAT is required, but not provided while calling.

Every PR has failed this check since this commit. It generates extra noise in emails.

[fufexan]

Oops. Okay, I'll fix it.

[memchr]

if: ${{ !startsWith(github.ref, "refs/pull/") && !endsWith(github.ref, "/merge") }}

[fufexan]

I came up with something like this

name: Nix

on: [push, pull_request, workflow_dispatch]

jobs:
  wlroots:
    if: github.event_name == 'push'
    uses: ./.github/workflows/nix-update-wlroots.yml
    secrets: inherit

  build:
    if: always() && !cancelled() && !contains(needs.*.result, 'failure')
    needs: wlroots
    uses: ./.github/workflows/nix-build.yml
    secrets: inherit

since we still want the packages to be built even if wlroots updating was skipped.