Going through the question, I believe that using the same repository for the different versions of Denodo Platform is not recommended. This is because some VQL statements of Virtual DataPort 8.0 and Virtual DataPort 7.0 may not be similar and this may lead to conflicts.
Further, I would suggest you to create a separate repository for each Denodo Platform version.
You can refer to the [Preparing to Upgrade](https://community.denodo.com/docs/html/browse/8.0/en/platform/upgrade/preparing_to_upgrade#virtual-dataport-create-a-repository-for-version-control) section and [Pre-Upgrade Tasks for the New Installation](https://community.denodo.com/docs/html/browse/8.0/en/platform/upgrade/pre_upgrade_tasks#virtual-dataport-version-control-system) section under Denodo Platform Upgrade Guide for more information.
Hope this helps !