You can see an example commit in the pureMD5 repo. New-Versions is a git trailer, they are documented in the official git documentation or at alchemists.io. Git trailers are part of the commit message. Github will show you the commit message in monospace type.
The point of this trailer is to communicate a temporary constraint to Cabal running in the CI system. It’s related to build-depends, since build-depends entries also typically have constraints on them. But New-Versions is used here for pinning to an exact version, which is the version that Renovate discovered. We want the CI suite to run with that exact version, because we want to find out whether the new release is compatible or not. If we didn’t have this additional constraint, the Cabal solver might not actually pick the new release. The modified build-depends entry as generated by Renovate will allow the newly released version, but it is wider than that, and in fact allows the whole major series that the new version is part of.
Does that clarify anything? I am still wondering how I can make this more appealing to e.g. new users reading the haskell-actions documentation. So if this message clarifies things for you, I’d love to hear if you have any suggestions on how I can make this as appealing as possible to readers of the haskell-actions documentation.