There isn't a "property migrator" but one can fairly easily take all the properties in site.conf created / modified after install and dump them into site.conf on the target and then just xconfmanager -p. This needs to be a key part of the upgrade process, not explicitly addressed as a "how-to" in the guides.
Note: If you do in fact have a custom Revision (version) series, then all the above applies. Need to be super careful to not overwrite what you intend to upload. The -read execution has to be to a different filename.