ChangeRequestSCMRevision has the equivalent(ChangeRequestSCMRevision) method that can be used to compare whether two revisions are the same ignoring the getTarget() but as BranchBuildStrategy does not have access to the previous revision we cannot use this method to allow an extension that would only build merge PRs when there are actual changes to the PR and ignore rebuilding because the target branch changed.

There are probably additional use cases, but this is sufficient to drive a solution.