duplicates of file paths not supported

[M1cha]

I'm trying to encapsulate an arch linux root directory but it fails like this:

$ ostree-ext-cli container encapsulate --repo repo/ latest containers-storage:bootc-arch
error: skopeo failed: time="2023-07-25T22:27:28+02:00" level=fatal msg="writing blob: adding layer with blob \"sha256:8d1a6cb92a36671bf05d40a886f5a9c97286cb0544b12ced16939f9b74757768\": processing tar file(): duplicates of file paths not supported"

[srd424]

I suspect this is something similar to canonical/rockcraft#203 ..