Jeff King [off-list ref] writes:

But really, I do not know that we need to NULL the whole thing. We have
given the caller the reduced argc. The only argv invariant we are
violating is that argv[argc] should be NULL (or in this case,
argv[left]). Anything after argv+left should be considered
uninitialized. So just:

  argv[left] = NULL;

would be enough, I'd think.

Even when strvec was passed and more than one element was eaten
after parsing?  strvec_clear() goes by .nr not stopping at the first
NULL IIRC.