One important feature of the Warnings Plugin is the classification of issues as new, outstanding and fixed. To compute this classification, the plugin requires a reference build (baseline). New, fixed, and outstanding issues are then computed by comparing the issues in the current build and in the baseline.

If this option is set, only issues that have been introduced in the current build are marked as new. Previously new issues in older builds will be converted to outstanding issues. I.e., if someone starts a new build manually (without source code changes), then no new issues will be in the job anymore.

By default, this option is disabled: then only a build is selected as reference that passed all quality gates. As soon as a build fails a quality gate, the reference will be frozen until all new issues are resolved again. That means, that new issues will be aggregated from build to build until the original reason for the failure, and all those additional new issues have been resolved. This helps much more to keep your project clean: as soon as there are issues, Jenkins will mark all builds as unstable until the issues have been resolved.