ggcr: crane.Export not handling whiteout files in single-layer images

[bcrochet]

Describe the bug

crane.Export has an optimization that skips the mutate.Extract call if there is only a single layer. However, it is possible to have an image that has opaque whiteouts in the only layer. While not usually a problem, there are other [1] libraries that expect there to be no hidden files, and therefore throw errors. When calling mutate.Extract, it works as expected.

To Reproduce

crane export quay.io/integreatly/3scale-bundle:v0.8.0 3scale.tar

This produces a tarball that still has .wh..wh..opq files.

Expected behavior

No .wh. files at all.

Additional context

I haven't figured this out yet, but I suspect that these .wh..wh..opq files are being generated by flattening a 2-layer image that is FROM scratch. Regardless, crane.Export should handle these. Currently it leaves them in place.

• latest version
• quay.io here, but observed with other registries