How to use GAE's dispatch.yaml with multiple development environments?

I know this is an old question, but I just discovered something interesting that will help everyone wanting to deploy to different environments. After a lot of trial and error, I figured out that gcloud requires the dispatch file given as parameter to be called dispatch.yaml. If you call it anything else, like dispatch-staging.yaml or dev-dispatch.yaml it won't work. However, and this is the trick I found, the file doesn't have to be in your project's root folder. So, in our project I did this:

1. <project_root>/dispatch.yaml - for production
2. <project_root>/deploy-staging/dispatch.yaml - for staging

And now I can do cd <project_root> and then:

1. gcloud --project <production> app deploy ./dispatch.yaml
2. gcloud --project <staging> app deploy ./deploy-staging/dispatch.yaml

In other words, gcloud doesn't care in what directory the dispatch.yaml file is located as long as it is called dispatch.yaml.

The way I approached this problem is by using different repo branches for the application code.

• the master branch version is deployed to my_app-dev - the development environment app
• the production branch version is deployed to my_app - the production environment app

This way the file is always named dispatch.yaml. The service names don't change between environments, but the custom domain names associated to them do - and that's reflected in the content of the dispatch.yaml file in the 2 branches:

$ git diff production master -- dispatch.yaml
diff --git a/dispatch.yaml b/dispatch.yaml
index 0768a6a..c1326cf 100644
--- a/dispatch.yaml
+++ b/dispatch.yaml
@@ -1,14 +1,14 @@
-application: my_app
+application: my_app-dev
 dispatch:
-  - url: "service1.my_app.com/*"
+  - url: "service1-dev.my_app.com/*"
     module: service1
-  - url: "service1-dot-my_app.appspot.com/*"
+  - url: "service1-dot-my_app-dev.appspot.com/*"
     module: service1
   - url: "*/service1/*"
     module: service1
-  - url: "service2.my_app.com/*"
+  - url: "service2-dev.my_app.com/*"
     module: service2
-  - url: "service2-dot-my_app.appspot.com/*"
+  - url: "service2-dot-my_app-dev.appspot.com/*"
     module: service2

Note: I'm implementing the different environments at the app level (as opposed to the service level, see Advantages of implementing CI/CD environments at GAE project/app level vs service/module level?). A service-level implementation cannot use this approach.