I'm trying to setup a pipeline through the AWS web console. The whole thing runs smoothly, but I have a problem with the varaibles outputted by CodeCommit that should be available to the following actions.
In the CodeCommit action configuration, the Variables namespace is set to SourceVariables.

In the CodeBuild action configuration, I defined a BRANCH environment variable supposed to map BranchName of the SourceVariables namespace, which should be outputted by the CodeCommit action based on this variable reference.

The BRANCH substitution works in CodeBuild... and yet.
This is hardly what I expected.
What am I missing in order to CodePipeline to value this environment variable from CodeCommit as expected?

