Identify pull request merge builds

[adamrbennett]

I have been watching this plugin and was excited to see the v1 release, thanks! I have high hopes for this plugin and its usefulness.

I'm using the GitHub Organization plugin with automatic job creation and webhooks.

Here's my workflow:

1. Open a PR -- PR build job created and run automatically
2. Merge PR into master -- master build job run automatically

When my PR build executes, I am able to access the pullRequest.merged property, and it is false as I would expect. However, when I merge the PR, and the master build runs, I am not able to access the pullRequest global variable (presumably because the build is executing against master, and not a PR).

I was hoping I would be able to check the pullRequest.merged property in the master build to determine that a PR has just been merged, and execute some additional logic. Is there another way to achieve this, should the approach above work, or is this just not supported at the moment?

[aaronjwhiteside]

You're right, the pullRequest global variable is only available in Pull Requests.

I'm afraid it wouldn't make much sense to make it available for ordinary branches.

What I think you're probably looking for is some kind of trigger for when a PR is closed/merged. Technically GitHub supports this t(https://developer.github.com/v3/activity/events/types/#pullrequestevent) so it should be possible to do. And I think the plumbing is already in place in the github-api/github plugin, we would just need to write a subscriber org.jenkinsci.plugins.github.extension.GHEventsSubscriber to listen for it.

If you feel up to it you could submit a PR, otherwise I'll add it to my todo list!

To answer your last question, this isn't currently supported by the Pipeline Github Plugin, but I think it would be a welcome addition.

As for is there a possible workaround, I think you might be able to check the branch history/log and determine if the latest commit was a merge commit and perhaps check the commit message, to determine the originating branch/pr.. I haven't tried to investigate this approach myself but a quick google found these:

• https://stackoverflow.com/questions/8475448/find-merge-commit-which-include-a-specific-commit
• https://github.com/mhagger/git-when-merged

I hope this gives you a starting point, otherwise I would really appreciate a PR.

[adamrbennett]

Thanks for the ideas. In the end, I just decided to use the commit hash and query the GitHub API:

def res = checkout scm
def commitHash = res['GIT_COMMIT']
withCredentials([usernameColonPassword(credentialsId: 'github-credentials', variable: 'AUTH')]) {
  pullRequestNumber = sh script: "curl -s -u $AUTH 'https://api.github.com/repos/<org>/<repo>/pulls?state=closed' | jq -j '.[] | select(.merge_commit_sha == \"$commitHash\") | .number'", returnStdout: true
}

I might still have a use for the PR trigger, though, and I started the initial work. If I get an opportunity to finish it, I'll submit a PR. Thanks for the help!

[l3ender]

Hello, we have this same desire (run job on a branch and be able to retrieve PR details for a merge to that branch). I am interested to contribute to the library but want to be sure the feature hasn't been added since this issue and that PRs would be accepted!

@aaronwalker - tagging you because I see you previously merged changes into this repo. Can you give your advice/thoughts?

[l3ender]

Also wondering if/how this PR relates to #91 - not sure if that is what is referenced by #1 (comment)?

What I think you're probably looking for is some kind of trigger for when a PR is closed/merged. Technically GitHub supports this t(https://developer.github.com/v3/activity/events/types/#pullrequestevent) so it should be possible to do. And I think the plumbing is already in place in the github-api/github plugin, we would just need to write a subscriber org.jenkinsci.plugins.github.extension.GHEventsSubscriber to listen for it.