v1.15.0

What's Changed

• Allow setting variables when using system packages by @TimoWilken in #795
• Warn about uncommitted files in final summary by @ktf in #798
• Make test_git work for privileged users by @ktf in #805
• Improve test support by @ktf in #806
• Abstract away SCM integration by @ktf in #803
• Add support for rhel9 by @Barthelemy in #808
• Use registry.cern.ch for Docker images by default by @TimoWilken in #793
• Add support for sapling by @ktf in #804

Full Changelog: v1.14.6...v1.15.0