The current behavior of -a (passing command line to the script via sys.argv is incompatible with that of vspipe, which makes portable scripts impossible.

Another drawback is that sometimes you will have to double escape the arguments (i.e. when passing a value including a \). I think vspipe's -a is much nicer, and we don't need to bother with using shlex.split to reparse the command line.

I have a rough patch ready, but, before sending it in, I'd like to gather some opinions on this issue as it's an incompatible change.