runScript method
Runs a script from the scripts map if it exists.
Implementation
Future<int> runScript(String script, {String extra = ''}) async {
final canonical = _resolveAlias(script);
final preScript = lookup('pre$canonical');
if (preScript != null) await _runScript('pre$canonical');
final exitCode = await _runScript(canonical, extra: extra);
final postScript = lookup('post$canonical');
if (postScript != null) await _runScript('post$canonical');
return exitCode;
}