The code in the linked GitHub repo was generated with a previous version of Amplication. The current version includes breaking changes that may cause conflicts when merged with code generated with previous versions.
The error indicates that there may be conflicts in the code generation that cannot be merged automatically.
Amplication is generating code in two separate layers of abstractions which allow the developers to freely customize their app with code on one layer without conflicting with the code generated by Amplication on the other layer.
While we are in beta, there may be some breaking changes in the design that will result in conflicts that need to be merged manually by the developer. This should rarely happen, but if you see this error - so this is one of these rare cases.
If you are not using any custom code in your app, it is easiest to delete the entire content of your repo before committing the changes, or just connecting the app with a new repo.
In case you already customized your app and added custom code, you can continue with committing your changes and manually resolve the conflicts; Amplication will create a new Pull Request in the repository and you will be able to compare the differences between the new Pull Request and the current state of the repo before merging the changes.
Amplication will never write directly to the main branch on the repo. You always get the chance to review the Pull Request before merging the changes.