Providing step output

[liiri]

Adding two new outputs to the Github action context:

• mergeResult - The result from the action run, could be one of skipped, not_ready, author_filtered, merge_failed, merged
• pullRequestNumber - If one or more pull requests were matched in the action this value will hold the Github number of one of them

The main motivation is to avoid the limitation of using the built in auth token. See also #36

For example:

name: automerge
on:
  ...
jobs:
  automerge:
    runs-on: ubuntu-latest
    steps:
      - name: automerge
        id: automerge
        uses: "pascalgn/automerge-action@v0.14.2"
        env:
          GITHUB_TOKEN: "${{ secrets.GITHUB_TOKEN }}"
      - name: feedback
        if: steps.automerge.outputs.mergeResult == "merged"
        run: |
          echo "Pull request ${{ steps.automerge.outputs.pullRequestNumber }} was auto merged!"

[pascalgn]

It's a lot of changes, I'm not so sure about this PR. Maybe we should start by just adding the output for some cases, directly in merge.js. Changing all the signatures to return a value doesn't seem to be the best way

[trent-abc]

This functionality is critical for us, if you're not going to accept the PR can you provide an alternative implementation?

[pascalgn]

Thanks a lot for the PR, this is merged now via #186! I've changed some things (therefore the new PR, I couldn't push to your branch), so if you're having any problems, feel free to create an issue! Thanks! 🚀