gitserver: Extract all regular files from NPM packages (!32320) · Merge requests · Warren Gifford / sourcegraph

Created by: tsenart

Context

This PR factors out .tar.gz unpacking into its own package, based off of https://github.com/gravitational/teleport/blob/master/lib/utils/unpack.go and uses it in gitserver to unpack NPM packages.

With this change we now handle more kinds of files and skip any we don't care about rather than erroring out.

Unit, integration and manual testing.