Implement the ability to auto-merge an arbitrary pull request

[roryabraham]

Fixed issue

Fixes #144

Details

This pull request introduces the ability to auto-merge an arbitrary pull request specified via three optional environment variables:

• PULL_REQUEST_NUMBER
• GITHUB_OWNER
• GITHUB_REPO

This will enable automerge-action to be used from a workflow that executes only on the workflow_dispatch event.

Note:
This is my first pull request in this repository, but I did my best to follow the code style and practices that you've established in this repo. Hopefully you find my work high-quality, but if not just let me know and I'll make whatever updates you suggest 😄 Thanks for the great work in this repo!

[pascalgn]

Sorry for responding so late to this PR!

I think it's fine, but I don't like it too much to have 3 different properties which can only be combined in a specific way. How about instead rename PULL_REQUEST_NUMBER to simply PULL_REQUEST and then let users put either 123 (simple PR number, defaults to the repo the action is running in) or pascalgn/test/123 (full PR specified)

WDYT?

[roryabraham]

How about instead rename PULL_REQUEST_NUMBER to simply PULL_REQUEST and then let users put either 123 (simple PR number, defaults to the repo the action is running in) or pascalgn/test/123 (full PR specified)

Yeah, that sounds reasonable to me! I will update this PR soon.

[roryabraham]

Okay, this PR is updated and ready for review 👍

[roryabraham]

@pascalgn friendly reminder that this is ready for review 🙂 Thanks!

[pascalgn]

Sorry for the delay and thanks for the PR, it's merged now! 👍