code: function copy (src, dest, dirname, done) {
        fsCompare.mtime(src, dest, function (err, diff) {
          if (err) return done(err)
          if (diff === 1) {
            if (fs.copyFile) fs.copyFile(src, dest, fin)
            else pump(fs.createReadStream(src), fs.createWriteStream(dest), fin)
          }
        })
        function fin (err) {
          if (err) return done(err)
          created(dirname, dest)
          done()
        }
      }
docs: Node <= 8.x does not have fs.copyFile(). This API is cool because on some OSes it is zero-copy all the way; e.g. never leaves the kernel! :D