dockerImageDestination.SupportedManifestMIMETypes may be incorrect

[mtrmac]

dockerImageDestination.SupportedManifestMIMETypes returns a hard-coded value; if the destination registry does not in fact support schema 2, we would still attempt to upload this.

This incorrect information will break any manifest conversion we might attempt.

[runcom]

We should probably test if V2 is really supported, otherwise fallback to push v2s1?

[mtrmac]

Yes. It would be very convenient if we could determine v2 support without having to create and try to push v2, I am not sure whether that is possible.

[runcom]

@mtrmac it should be easy https://github.com/docker/docker/blob/master/distribution/push_v2.go#L159-L193

[mtrmac]

Yeah, that is the “convert and try” method which I’d like to avoid :)

[runcom]

Yeah, that is the “convert and try” method which I’d like to avoid :)

can it work with this "convert and try" though?

[mtrmac]

Yeah, that is the “convert and try” method which I’d like to avoid :)

can it work with this "convert and try" though?

Sure, it is software, we can build anything we can specify. But with the increasing number of formats (schema1, schema2, OCI, perhaps even native Docker tar exposed to copy.go), the conversion engine will need to do a series of false starts instead of just statically detecting the optimal destination format and doing a single conversion. Doable but ugly.

[mtrmac]

#88 implements the “convert and try” method. At least with the OpenShift acceptschema2 option, there is no way to tell what is supported other than try to push a manifest.