code: function updateHeader(fileInfo, data, type, headerLineRegex, options) {
    const contents = fs.readFileSync(fileInfo.path, 'utf8') || ''
    const body = contents.split('\n')
    // assumes all comments at top of template are the header block
  
    const preheader = []
    while (body.length && !body[0].trim().match(headerLineRegex)) preheader.push(body.shift())
    while (body.length && body[0].trim().match(headerLineRegex)) body.shift()
  
    const template = renderTemplate(data, type, options)
    const header = []
    for (let hline of template.split('\n')) {
      if (!hline.trim().match(headerLineRegex)) break
      else header.push(hline)
    }
    const newContents = preheader.concat(header).concat(body).join('\n')
    fs.writeFileSync(fileInfo.path, newContents)
  }
docs: Keeps the header block of your templated file in sync with your Swagger api.
  
  @param {object} fileInfo info on the file to target
  @param {object} data the operation which to gen the header from
  @param {string} type the type of file being updated
  @param {regex} headerLineRegex regex to find if a line is part of the header
  @param {object} options options containing details on rendering the header
  @return {void}