Add `backported` label to PRs when running the backport tool

[sqren]

Add `backported` label to PRs when running the backport tool

[sqren]

@brianmcgue Yes, this is exactly how I determine which commits have been backported:

This approach is also tells whether a backport PR has been created (grey) or merged in (green); and to which versions.
I was thinking of extracting this logic, so we can have a daily job that verifies that all PRs to master are backported within 48 hours or something like it. And post a comment on the PR if a backport is missing.

@spalger I've created a PR that adds the option backport-created-labels (I'm open to better naming suggestions).

[FrankHassanabad]

That sounds like an improvement so ++

[acrewdson]

+1 for this and also for making the label name configurable in config.json

[sqren]

Cool, what do you think the option should be called? There is already labels which are the labels added to the backport PRs:

// Example .backportrc.json
{
  "upstream": "elastic/kibana",
  "branches": [{ "name": "7.x", "checked": true }, "7.4", "7.3"],
  "labels": ["backport"]
}

I was thinking about originalPRLabels, statusLabels, successLabels, postBackportLabels. None of them are great. Input much appreciated.

[acrewdson]

originalPRLabels seems pretty good to me, but yeah, it's a tough one

[brianmcgue]

GitHub's reference links are useful when it comes to this. And since each commit message in the PR references its original PR, they should always show up. But this would still be useful when filtering PRs and for quick reference checks 👍