def usage_hint(command, shell):
    """
    Returns the usage hint and comment, for the given shell.
    """
    if shell == "fish":
        return ("eval ({command})".format(command=command), "#")
    elif shell == "powershell":
        return (
            "{command} | ForEach-Object {{If (-Not[string]::IsNullOrEmpty($_)) {{ $_ | Invoke-Expression }}}}".format(
                command=command
            ),
            "#",
        )
    elif shell == "cmd":
        return (
            '\t@FOR /f "tokens=*" %i IN ({command}) DO @%i'.format(command=command),
            "REM",
        )
    elif shell == "emacs":
        return (
            "(with-temp-buffer (shell-command {command} (current-buffer))"
            "(eval-buffer))".format(command=command),
            ";;",
        )
    elif shell == "tcsh":
        return ("eval `{command}`".format(command=command), ":")
    else:
        return ("eval $({command})".format(command=command), "#")