def _append_project(issue_ids, project_name):
  """Append project name to convert <id> to <project>:<id> format."""

  result = []
  id_list = issue_ids.split()
  for id_str in id_list:
    if ':' in id_str:
      result.append(id_str)
    # '-' means this issue is being removed
    elif id_str.startswith('-'):
      result.append('-%s:%s' % (project_name, id_str[1:]))
    else:
      result.append('%s:%s' % (project_name, id_str))
  return result