code: function lastRelease() {
    const {stdout: branches} = exec(`git branch -a | grep 'origin/release'`)
    const releases = branches.
      split("\n")
      .map(b => b.replace(/remotes\/origin\//, '').trim())
      .filter(b => b.match(/^release-(\d+)$/))
  
    const ordered = sortBy(releases, r => parseInt(/\d+/.exec(r)[0], 10)  )
    return ordered[ordered.length -1];
  }
docs: searches the git branches for the last release branch