I'm setting up an automated deployment of a web site in VSTS to Azure using the "Azure Web App Deployment" task. I have set up deployments in the past where the Web App Name was static for a particular target environment, but for this particular project, I'd like for the Web App Name to be calculated (in part) from a property determined at build time: the branch name, via the $(RELEASE_ARTIFACTS_CI_BUILD_SOURCEBRANCHNAME) variable. However, the Web App Name property of the "Azure Web App Deployment" task does not seem to expand server variables - it seems to expect and enforce a static value here.
I've also tried setting the -Name switch under Additional Parameters, but that seems to be overridden by the Web App Name I had to specify.
My question: is it possible to have the Web App Name calculated from server variables at the time of deployment, and if so, how is this done?