It's actually surprisingly awkward to figure out if a system is affected; the best I can come up with is

    SVNVER=`uname -v | cut -f 4 -d ' ' | cut -c 2-7`
    if [ $SVNVER -ge 273872 ] && [ $SVNVER -lt 278907 ]; then
        echo buggy RNG
    fi

But even that doesn't answer the important question -- what matters is not whether you are on a buggy system but rather whether your keys were generated on a buggy system. And there's no practical way to figure that out programmatically.

I'd also probably mention that this affects very few Tarsnap users earlier. First sentence early.

Fair enough. I'm good at memory dumps, not so good at figuring out which bits are most important.