As part of processing a backport-style pull request, Skara checks whether the patch for that PR is "clean", meaning the patch is identical to the original commit being backported, and adds a "clean" label to the PR.

Currently, a clean backport can be integrated without review, which makes sense for many repos / code lines, but might not be desirable for others. For example, we might consider requiring a review for a clean backport to the jdk (or jfx) feature release during rampdown for that release.

We should add the ability to control whether reviews are required for clean backports, either as a Skara configuration attribute or a jcheck attribute. The default should be "no review required" to match current behavior.

Once this enhancement is implemented, we can separately decide whether to require reviews for some repos.