Generate diff reports to pinpoint regression

[vmassol]

Use case:

• On XWiki we fail the build when the mutation score decreases under a given threshold
• However, it's not easy to fix the decreased mutation score and to know what made it go down.

Thus it would be nice if Descartes could have some way to generate a diff report, showing only the diff between the execution before the threshold failure and the execution after the threshold failure.

Or maybe you have some idea how we can pinpoint the regression?

Thanks