Update the GitHub Actions container to allow users to pass a cloud url (#4243)

CHANGELOG.md

@@ -5,6 +5,9 @@ CHANGELOG
 - Fix error related to side-by-side versions of `@pulumi/pulumi`.
   [#4235](https://github.com/pulumi/pulumi/pull/4235)
 
+- Allow users to specify an alternate backend URL when using the GitHub Actions container with the env var `PULUMI_BACKEND_URL`.
+  [#4243](https://github.com/pulumi/pulumi/pull/4243)
+
 ## 1.13.1 (2020-03-27)
 - Move to a multi-module repo to enable modules for the Go SDK
   [#4109](https://github.com/pulumi/pulumi/pull/4109)

dist/actions/entrypoint.sh

@@ -3,6 +3,12 @@
 
 set -e
 
+# The default backend URL is the Pulumi Managed Service.
+# To use one of the alternate supported backends, set the
+# PULUMI_BACKEND_URL env var according to:
+# https://www.pulumi.com/docs/intro/concepts/state/#to-a-self-managed-backend.
+pulumi login $PULUMI_BACKEND_URL
+
 # If the PULUMI_CI variable is set, we'll do some extra things to make common tasks easier.
 if [ ! -z "$PULUMI_CI" ]; then
     # Capture the PWD before we go and potentially change it.