On this document:

https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/8-beta/html/using_jboss_eap_on_openshift_container_platform/assembly_building-and-running-jboss-eap-applicationson-openshift-container-platform_default#proc_building-applications-images-using-source-to-image-s2i-on-openshift_assembly_building-and-running-jboss-eap-applicationson-openshift-container-platform

there is a following example of a helm.yaml document:

build:
  url: https://github.com/jboss-developer/jboss-eap-quickstarts.git
  ref: EAP_8.0.0.Beta
  contextDir: helloworld
deploy:
  replicas: 1

There is a typo, the "url" key should in fact be "uri".

The difference is important, the current notation makes the deployment process disfunctional: Instead of the URI given by user, a default URI is used which points to completely different repo, so a user would either deploy a different application, or the deployment fails because the default repo doesn't contain branch/tag that the user specified.

Note that the link to document I provided above is for 8-beta version, I don't know if there is newer version of the document. I don't see any other version available ATM.