Hey Saintthor,
"
gcloud app deploy" has gone out of beta into general availability as the recommended method to deploy apps. You can read the documentation
here.
As far as downloading the app's code, you can use the
gcloud source command tree if you have your code in the Cloud Source Repo for the project.
If you're the original developer, you could also have a copy of the code somewhere else.
Finally, you can still use the "appcfg download_app" command to download the source from a deployed app.
I hope this has helped. Let me know if you have any questions!
Cheers,
Nick
Cloud Platform Community Support