How about this: collect a list of (variant, arch, name) for both composes and then display the difference (with complete version and release).

That would provide information like oOld compose had fedora-server-base-24-1 image in Server.x86_64, but there is no fedora-server-base in new compose.* or vice versa.

I'm not sure it makes sense to display that just the version number of the same image changed, because that is expected and will happen always. We don't report bumped version on other images either. Since the contents of the image should be based on the RPMs in the compose anyway, that should kind of tell you what changed in the image.

Thanks Lubomír. The reason I was interested in the Koji task IDs and getTaskInfo is that I want to compare two scratch builds to each other in order to find out the dist-git Git sha1s they were built from.

I see now that OSBS embeds this information into the container image's LABELs ("vcs-ref" LABEL). So I could get that Git information from OSBS.

semi-related ticket: formalizing container metadata in composes https://github.com/release-engineering/productmd/issues/91

We might look into this tool Google's just released: https://opensource.googleblog.com/2017/11/container-diff-for-comparing-container-images.html