WIP Allow running a tainted runner

[JRaspass]

STILL WIP. DO NOT MERGE

This allows tainted tests to benefit from the preload feature, fixes #262.

[exodist]

I am not bothered by the untaint, this proof of concept looks good. It will need a t/integration test that verifies it, as well as the cleanup and polish you already mentioned needing.

The one thing I would change about untaint() is that I would make it so that at load time it checks if taint mode is enabled, if it is then define sub untaint as you have, but if taint mode is not enabled just return the argument and skip the regex, as a minor performance enhancement when taint is not used.

The test is essential becaus eI will almost certainly break this feature without a test to save me from that. The test should skip on platforms/perls where taint mode is not available.

[JRaspass]

@exodist So I've tried writing an integration test for this but I'm kinda stuck. I'm basing it on t/integration/preload.t as I feel that's the closest to what I'm trying to test (basically that files are still preloaded for tests ran under taint mode but tainting the runner).

yath(
    command => 'test',
    args    => [$dir, '--ext=tx', '--taint', '-A', '-PTestTaintPreload'],
    exit    => 0,

But I quickly ran into problems, it appears the entire yath script is running under taint mode and not just the runner, I tried adding various "fixes" like this but kept running into insecure dependencies under -T so I'm not really sure how best to proceed.

                # Avoid loading File::Glob in this process...
                ($path) = $path =~ /(.*)/;
                ($val)  = $val  =~ /(.*)/;
                ($^X)   = $^X   =~ /(.*)/;
                warn "$path$val";
                warn "$^X";
                delete local $ENV{PATH};
                my $out = `$^X -e 'print join "\\n" => glob("${path}${val}")'`;

Does App::Yath::Tester do something different to just calling yath test --taint ... on the command line? What we really want is the yath process to be untainted, the runner to be tainted, and all forked children to be tainted.

I'm also wondering if we need a --taint-warnings flag or something to match perl -t, it still feels kinda hacky to have to pass the right flag to the runner to match the bulk of your tests.

[exodist]

I have to consider this for a while. I am not sure of the best way to handle this..