[results feed] Add staging branch to build configuration

Change-Id: If1efbd5a8733cf5ba12b899e5ec5c34a1ad36059
Reviewed-on: https://dart-review.googlesource.com/c/dart_ci/+/157762
Reviewed-by: William Hesse <whesse@google.com>
Commit-Queue: Karl Klose <karlklose@google.com>
diff --git a/functions/build.yaml b/functions/build.yaml
index 9d395ab..88a03a3 100644
--- a/functions/build.yaml
+++ b/functions/build.yaml
@@ -10,5 +10,6 @@
         options:
           compiler: dart2js
           # List any dart2js specific args here, or omit it.
-          dart2js_args: []
-          # - --minify
\ No newline at end of file
+          dart2js_args:
+          - -DSTAGING_BRANCH=ci-test-data
+          # - --minify
diff --git a/functions/node/commits_cache.dart b/functions/node/commits_cache.dart
index 296bc30..1eeaf9c 100644
--- a/functions/node/commits_cache.dart
+++ b/functions/node/commits_cache.dart
@@ -99,7 +99,7 @@
 
   Future<String> get branchName async {
     if (await firestore.isStaging()) {
-      return const String.fromEnvironment('BRANCH') ?? 'master';
+      return const String.fromEnvironment('STAGING_BRANCH') ?? 'master';
     }
     return 'master';
   }