helixDnaRunner function
The gg dna runner used outside of tests: helix's own commands, with
the prompts of the gg suite — what gg dna itself runs.
Implementation
RunDna helixDnaRunner(GgLog ggLog) {
final runner = CommandRunner<dynamic>('gg', 'gg')
..addCommand(_DnaCommand(ggLog: ggLog));
return (args) => runner.run(['dna', ...args]);
}