How to list the last PR merged to a branch

[abhimeht23]

Hi @gr2m / @timrogers ,

Is there an API that gives detail of the last pull request that was merged to "main" or "master" branch? For my application I want to know the last pull request that was merged into master branch.

Thanks,
Abhi

[oscard0m]

Hi @abhimeht23!

Thanks for opening this discussion.

Your question is more related to what options GitHub API gives the users than how to make that REST/GraphQL API Request with Octokit.

I think your question can be better addressed in GitHub Discussions: API and Webhooks.

If you decide to post there, feel free to @mention me. I would be happy to track and give my input on it to help you discover this with GitHub Community.

---

My quick research

Taking a quick look, I've found a way to get the last UPDATED Pull Request with the state MERGED to a particular baseBranch.

But, to be the most recent Pull Request updated does not necessarily mean it is the most recent merged one (it can have a new comment or a new label after weeks of being merged, for example).

Here's the GraphQL query I run in GitHub's GraphQL Explorer, in case it can be useful to you:

query { 
  repository(owner: "oscard0m", name: "web") { 
    pullRequests(states: MERGED, first: 1, orderBy: { field: UPDATED_AT, direction: DESC }, baseRefName: "main") {
      nodes {
        title,
        merged,
        updatedAt,
        mergedAt,
        url,
        headRefName,
        baseRef {
          name
        }
      }
    }
  }
}

output

{
  "data": {
    "repository": {
      "pullRequests": {
        "nodes": [
          {
            "title": "chore(deps): update dependency eslint to v8.21.0",
            "merged": true,
            "updatedAt": "2022-08-11T10:55:30Z",
            "mergedAt": "2022-08-01T10:19:45Z",
            "url": "https://github.com/oscard0m/web/pull/232",
            "headRefName": "renovate/eslint-8.x",
            "baseRef": {
              "name": "main"
            }
          }
        ]
      }
    }
  }
}

As you can see, the mergedAt and updatedAt do not have to match necessarily.

[timrogers]

👍🏻 on what @oscard0m said! Another option here would be to use the "List commits" API. If a PR is merged through the GitHub UI, then you will have a commit with a message like this:

"Merge pull request #739 from restforce/dependabot/bundler/webmock-tw-3.17.1\n\nUpdate webmock requirement from ~> 3.16.0 to ~> 3.17.1"

You can see an example if you fetch the latest commits for restforce/restforce.