def METHOD_NAME(cwd, rev="tip", short=False, user=None):
    """
    Returns the long hash of a given identifier (hash, branch, tag, HEAD, etc)
    cwd
        The path to the Mercurial repository
    rev: tip
        The revision
    short: False
        Return an abbreviated commit hash
    user : None
        Run hg as a user other than what the minion runs as
    CLI Example:
    .. code-block:: bash
        salt '*' hg.revision /path/to/repo mybranch
    """
    cmd = ["hg", "id", "-i", "--debug" if not short else "", "-r", "{}".format(rev)]
    result = __salt__["cmd.run_all"](cmd, cwd=cwd, runas=user, python_shell=False)
    if result["retcode"] == 0:
        return result["stdout"]
    else:
        return ""