code: async function add(files) {
  	const shell = await execa('git', ['add', '--ignore-errors'].concat(files), {reject: false});
  	debug('add file to git index', shell);
  }
docs: Add a list of file to the Git index.
  If on of the files is present in the .gitignore it will be silently skipped. Other files will still be added.
  
  @param {Array<String>} files Array of files path to add to the index,