Can't import images compressed with zstd

[lukeyeager]

See moby/moby#41759. This is a new feature in docker 23.0.

$ enroot import docker://gscrivano/zstd-chunked:fedora33
[INFO] Querying registry for permission grant
[INFO] Authenticating with user: <anonymous>
[INFO] Authentication succeeded
[INFO] Fetching image manifest list
[INFO] Fetching image manifest
[INFO] Downloading 2 missing layers...

100% 2:0=0s 3fcb8d545795d85012fdfb10c2428e07ff1a2c0f81fd5ac23e01f4cf0bfeecbc

[INFO] Extracting image layers...

0% 0:1=0s 17909b5b15f7d5bfd14401387f8e32c1407bed336b233e857371799c891649f1
tar: This does not look like a tar archive
tar: Skipping to next header
tar: Exiting with failure status due to previous errors
100% 1:0=0s 17909b5b15f7d5bfd14401387f8e32c1407bed336b233e857371799c891649f1

[3XX0]

Not optimal because it will recompress unnecessarily, but you can do:
ENROOT_GZIP_PROGRAM=zstd enroot import docker://gscrivano/zstd-chunked:fedora33

Or set the option in enroot.conf

[lukeyeager]

Oh, neat workaround! Shall I leave this open so we can decide to improve things later (if zstd images become more common)?

[3XX0]

Yeah I think we can always improve it down the road

[krono]

Am I reading that right that import is actually downloading, expecting gzip and then zstd'ing anyways just to unzstd during extraction?
So the option here would be to do nothing on download?

[3XX0]

Yeah, the enroot cache is expected to be compressed in zstd, since most Docker images are gzipped we convert it.
So the above hack uncompress/recompress unnecessarily, we should just skip it if we detect the zstd MIME.