cmd: ensure create_full_path returns FALSE for all errors

[Dan Kegel]

2011/6/4 Frédéric Delanoy <frederic.delanoy at gmail.com>:
> BTW, there's a
> +rem warning, don't run any tests that depend on %ErrorLevel% after this line
> in your patch
>
> Is there really no way to reset ErrorLevel to a sane value?

It's more subtle than that.  That section of code checks what
happens when you try to set an environment variable named
ErrorLevel, which is kind of a no-no; real world batch files
shouldn't be doing that, as it doesn't do what one expects.

> IMHO it makes more sense to use tests using ErrorLevel *after* its
> correct behaviour has been demonstrated, if possible...

Order should not be important, IMHO.  We ought to be running
each of those sections in its own little cmd session.  That
would prevent test failures from cascading into the next section.
- Dan