complain if a version is appended to version.json

[mvdan]

I reviewed and approved ipld/go-codec-dagpb#37 to bump the semver bugfix version, and it worked when merged - the tag appeared etc. I just didn't notice that the git diff was adding one object key-value, rather than replacing the existing one.

I get that, semantically, it's the same - when decoding, the second key-value wins. Still, to avoid confusion, I think the versioning workflow should reject any version.json that isn't exactly an object with one version key.

[marten-seemann]

This could be part of the release-checker workflow. It could then report a malformed version.json on the PR.

[galargh]

This issue was transferred to ipdxco/unified-github-workflows#41 in preparation for archiving of this repository.