tools/android/loading Add instructions to deploy to staging frontend.

tools/android/loading/cloud/frontend/README.md

 # Appengine Frontend for Clovis
 
 [TOC]
 
 ## Usage
 
 Visit the application URL in your browser, and upload a JSON dictionary with the
 following keys:
 
 -   `action` (string): the action to perform. Only `trace` and `report` are
@@ skipping 106 matching lines @@
 
 ### Deploy
 
 ```shell
 # Install dependencies in the lib/ directory.
 pip install -r requirements.txt -t lib
 # Deploy.
 gcloud preview app deploy app.yaml
 ```
 
+To deploy to a staging/test version of the server, you can do:
+
+```shell
+gcloud preview app deploy --no-promote --version $MY_VERSION
+```
+
+where `MY_VERSION` can be something like `staging` or something more unique to
+ensure there is no name collision. You can then access the application live on
+the web by prefixing the URL of the service with `$MY_VERSION-dot-`.
+
 ### Updating the Database Schema
 
 When a change is made to the dictionary returned by report.py, the BigQuery
 database schema must be updated accordingly.
 
 To update the schema, run:
 
 ```shell
 bq update \
   --schema \
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 [1]: https://cloud.google.com/sdk
 [2]: https://cloud.google.com/appengine/docs/python/taskqueue
 [3]: https://cloud.google.com/appengine/docs/python/config/queue
 [4]: ../backend/README.md#Deploy-the-code
 [5]: https://cloud.google.com/appengine/docs/python
 [6]: http://flask.pocoo.org
 [7]: #Updating-the-Database-Schema
 [8]: https://bigquery.cloud.google.com