bug#57949: git head; unportable test(1) operator

[Gregory Heytings]

> > If it's problematic to have zero-width space characters there, they 
> > could be removed and/or replaced by something else.
>
> Depending on how you view them, they could appear as "<U+200B>", in 
> inverse video, on a terminal's display.  Which stands out and gets in 
> the way of reading.

Indeed.  I've now changed the way the message is displayed, it now uses 
three leading stars and is redirected to stderr, which is e.g. what the 
Linux kernel uses.