Add PR number to Image Build Tag

Author: Odilhao

.tekton/foreman-proxy-develop-push.yaml

@@ -459,6 +459,8 @@ spec:
         value: $(tasks.build-image-index.results.IMAGE_URL)
       - name: IMAGE_DIGEST
         value: $(tasks.build-image-index.results.IMAGE_DIGEST)
+      - name: ADDITIONAL_TAGS
+        value: $(params.additional-tags[pull-request-{{pull_request_number}}])
       runAfter:
       - build-image-index
       taskRef: