Hyperdrive allows files to be written as subpaths of other files

[pfrazee]

It's currently possible to do this:

var archive = hyperdrive('/tmp')
archive.writeFile('/foo', 'content', (err) => {
  archive.writeFile('/foo/bar', 'more content', (err) => {
    // done
  })
})

Is that a problem?

[mafintosh]

We might wanna disallow that in the future but yea that works right now.