There are articles stating how to upgrade an MSI package using WIX here, and here, but for automated integration builds this may not work. Specifically, those articles state that we need to provide the previously install GUID along with a new one. Sounds like the build system needs to start tracking installed/generated GUIDs - which is not desirable.
Ideally, we would just update the product version (e.g. 1.0.0 to 1.1.0, etc) and msiexec would perform the upgrade with just that. This may not work, but you get the idea. Has anyone managed to get an automated build of MSI that's upgradeable if it's installed automatically as well?
Note: I say that tracking installed GUIDs are not preferred since typically the build system should not care what was there before (e.g. uncompressing ZIP files and using that). Any guidance would be appreciated.