ci: fix changelog generation for tag events (#8)

.woodpecker/build-package.yml

@@ -22,8 +22,8 @@ steps:
     commands:
       - git fetch --depth=2147483647
       - git sv current-version
-      - git sv release-notes
-      - git sv release-notes -o CHANGELOG.md
+      - git sv release-notes -t ${CI_COMMIT_TAG:-next} -o CHANGELOG.md
+      - cat CHANGELOG.md
 
   publish-github:
     image: docker.io/plugins/github-release