fix: ignore forks

[laurentsenta]

Contributes to #249

When working with the GitHub API, a run originating from a fork might still have the same branch name (e.g., master) as the parent repository. To filter out runs from forks, we check the head_repository attribute of the run. This attribute contains information about the repository where the head of the pull request is stored.

[dawidd6]

Nice but I think this should be guarded by a new action input, defaulting to false, as it could break some existing workflows based on PRs I guess.

[laurentsenta]

I would recommend against making it default, there is no way someone writing the following code intended to load artifacts from any fork from the internet:

- name: Download artifact
  id: download-artifact
  uses: dawidd6/action-download-artifact@v2
  with:
    branch: master

We wouldn't have caught it if our target workflow didn't require approval on the first run.

What do you want the input name to be?

[laurentsenta]

proposed a version that might work for both of us, I'm testing it out right now; let me know if that model works for you. Otherwise I'll do the simple flag.

[laurentsenta]

Ready for merge, used in yaml, run

DOWNLOAD JSON OUTPUT
==> Repository: ipfs/kubo
==> Artifact name: gateway-conformance.json
==> Local path: ./
==> Workflow name: gateway-conformance.yml
==> Branch: master
==> Allow forks: false
...
==> Skipping run from fork: patrickReiis/kubo
==> Skipping run from fork: patrickReiis/kubo
...

[dawidd6]

Very nice. Thanks for contribution!