comment-run-merge-preview.js

(async () => {
  // Get pull-req URL like "https://api.github.com/repos/nwtgck/actions-merge-preview/pulls/4"
  const pullReqUrl = context.payload.issue.pull_request.url;
  const githubUser = context.payload.repository.owner.login;
  console.log({ githubUser });
  const res = await fetch(pullReqUrl, {
    headers: [
      ['Authorization', `Basic ${Buffer.from(`${githubUser}:${githubToken}`).toString('base64')}`]
    ]
  });
  const resJson = await res.json();
  const prUserName = resJson.head.user.login;
  const baseBranchName = resJson.base.ref;
  const branchName = resJson.head.ref;
  const fullRepoName = resJson.head.repo.full_name;
  const previewBranchName = `actions-merge-preview/${prUserName}-${branchName}`;
  execSync(`git config --global user.email "bee-bot-bot@protonmail.com"`);
  execSync(`git config --global user.name "Bee Bot"`);
  // (from: https://stackoverflow.com/a/23987039/2885946)
  execSync(`git fetch --all`);
  console.log(execSync(`git checkout ${baseBranchName}`).toString());
  console.log(execSync(`git checkout -b ${previewBranchName} ${baseBranchName}`).toString());
  console.log(execSync(`git pull https://github.com/${fullRepoName}.git ${branchName}`).toString());
  // Push preview branch
  // NOTE: Force push (should be safe because preview branch always start with "actions-merge-preview/")
  execSync(`git push -fu origin ${previewBranchName}`);
  const baseRepoFullName = context.payload.repository.full_name;
  // Create GitHub client
  const githubClient = new GitHub(githubToken);
  // Comment body
  const commentBody = `🚀 Preview branch:  \n<https://github.com/${baseRepoFullName}/tree/${previewBranchName}>`;
  // Comment the deploy URL
  await githubClient.issues.createComment({
      issue_number: context.issue.number,
      owner: context.repo.owner,
      repo: context.repo.repo,
      body: commentBody
  });
})();