commit-message.yaml

name: 'Commit Message Check'
on:
  pull_request_target:
    types:
    - opened
    - reopened
    - synchronize

jobs:
  check-commit-messages:
    name: Check Commit Messages
    runs-on: ubuntu-latest
    steps:
    - name: Block mentions
      uses: actions/github-script@v4
      with:
        github-token: ${{ secrets.GITHUB_TOKEN }}
        script: |
          const commits = await github.pulls.listCommits({
            owner: context.repo.owner,
            repo: context.repo.repo,
            pull_number: context.issue.number
          });

          const mentionRegex = /(^| )@([a-z\d](?:[a-z\d]|-(?=[a-z\d])){0,38})/gmi;
          let mentioningCommitShas = [];

          for (const commit of commits.data) {
            while (match = mentionRegex.exec(commit.commit.message)) {
              const mention = match[2];

              // check if detected mention is actually a github username
              try {
                const user = await github.users.getByUsername({
                  username: mention,
                });
                if (user.data.login == mention) {
                  mentioningCommitShas.push(commit.sha);
                }
              } catch (err) {
                if (err.status != 404) {
                  throw err;
                }
              }
            }
          }

          if (mentioningCommitShas.length == 0) {
            core.info("no commit messages with mentions detected");
            return;
          }

          errMsg = `This PR contains commits including \`@mentions\` in the commit message: ${mentioningCommitShas.join(", ")}\n`+
            `Please remove the mentions from the commit messages to prevent notifying the mentioned users every time the commit is pushed to some fork of this repository.`;

          await github.issues.createComment({
            issue_number: context.issue.number,
            owner: context.repo.owner,
            repo: context.repo.repo,
            body: `@${context.payload.pull_request.user.login} ` + errMsg
          });

          core.setFailed(errMsg);