The 'check-patch.sh' script in the 'jenkins' repo knows how to generate a 'differences.html' file when job YAML changes.

The 'jenkins' repo is designed to be used as an upstream source repo for other repos, and it is designed that 'check-patch.sh' will be usable on those DS repos.

When YAML changes from the 'jenkins' repo make it into the DS repos via a patch to the 'upstream-sources.yaml' file in the DS repo, and 'check-patch.sh' runs on that repo, 'differences.html' is not being generated, because the change to 'upstream-sources.yaml' does not look like a job YAML change.

We need to change 'check-patch.sh' so that when running in a DS repo, it knows how to look and diagnose changes coming from the upstream repo.