Manifest publishing support for duplicated platforms

[mthalman]

With the changes being done for dotnet/dotnet-docker#2182, it will cause a platform to be defined multiple times in a manifest, contained in separate images. This requires changes to PublishManfiestCommand in order to correctly handle this scenario because it will otherwise throw an exception when it encounters a platform with no concrete platform tags.

This is solved by finding the matching platform that does contain a concrete tag and using that as the reference tag for the manifest creation.

[mthalman]

Moving this to draft because I found some issues that need fixing.

[mthalman]

I've also fixed an issue I found with the merging of image info content. Duplicated platforms contained in separate images were being detected as equal in PlatformData.Equals. This meant there content would be merged together instead of kept in separate images.

The solution is not great. It now takes into account the convention a duplicated platform will not have simple tags defined for it. When one platform has simple tags and another does not, they are now considered to not be equal regardless of whether they having a matching Dockerfile, platform, etc.

[MichaelSimons]

Seeing this issue triggered me to question if the IngestKustoImageInfoCommand is going to handle this situation. I think it should but can you take a look if you haven't already to ensure the correct info is getting ingested?

[mthalman]

Seeing this issue triggered me to question if the IngestKustoImageInfoCommand is going to handle this situation. I think it should but can you take a look if you haven't already to ensure the correct info is getting ingested?

It would result in duplicate digest lines outputted. Is that ok?

[MichaelSimons]

Seeing this issue triggered me to question if the IngestKustoImageInfoCommand is going to handle this situation. I think it should but can you take a look if you haven't already to ensure the correct info is getting ingested?

It would result in duplicate digest lines outputted. Is that ok?

Yes, duplicated digests will be alright.