empty string?

.azure-pipelines/release.yml

@@ -8,9 +8,10 @@ pr: none
 
 stages:
   - template: templates/stages/test-and-package-stage.yml
+    parameters:
+      dockerTag: ${{variables['Build.SourceBranchName']}}
   - template: templates/stages/changelog-stage.yml
   - template: templates/stages/deploy-stage.yml
     parameters:
       snapReleaseChannel: beta
-      dockerTag: ${{variables['Build.SourceBranchName']}}
   - template: templates/stages/notify-failure-stage.yml

.azure-pipelines/templates/jobs/packaging-jobs.yml

@@ -1,12 +1,17 @@
+parameters:
+- name: dockerTag
+  type: string
+
 jobs:
+  # If this job name is changed, the value of builtDockerTag in the deploy
+  # stage needs to be updated.
   - job: docker_build
     pool:
       vmImage: ubuntu-18.04
     steps:
       - bash: |
-          docker images
-          tools/docker/build.sh nightly
-          docker images
+          tools/docker/build.sh ${{ parameters.dockerTag }}
+          echo "##vso[task.setvariable variable=builtDockerTag;isOutput=true]${{ parameters.dockerTag }}"
         displayName: Build the Docker images
   - job: installer_build
     pool:

.azure-pipelines/templates/stages/deploy-stage.yml

@@ -5,9 +5,6 @@ parameters:
   values:
   - edge
   - beta
-- name: dockerTag
-  type: string
-  default: nightly
 
 stages:
   - stage: Deploy
@@ -65,23 +62,8 @@ stages:
       - job: publish_docker
         pool:
           vmImage: ubuntu-18.04
+        variables:
+          builtDockerTag: $[ stageDependencies.TestAndPackage.docker_build.outputs['foo.bar'] ]
         steps:
-          - task: Docker@2
-            inputs:
-              command: login
-              # The credentials used here are for the shared certbotbot account
-              # on Docker Hub. The credentials are stored in a service account
-              # which was created by following the instructions at
-              # https://docs.microsoft.com/en-us/azure/devops/pipelines/library/service-endpoints?view=azure-devops&tabs=yaml#sep-docreg.
-              # The name given to this service account must match the value
-              # given to containerRegistry below. "Grant access to all
-              # pipelines" should also be checked.  To revoke these
-              # credentials, we can change the password on the certbotbot
-              # Docker Hub account or remove the account from the
-              # Certbot organization on Docker Hub.
-              containerRegistry: docker-hub
-            displayName: Login to Docker Hub
-          - bash: tools/docker/build.sh  ${{ parameters.dockerTag }}
-            displayName: Build the Docker images
-          - bash: tools/docker/deploy.sh ${{ parameters.dockerTag }}
+          - bash: echo $(builtDockerTag)
             displayName: Deploy the Docker images

.azure-pipelines/templates/stages/test-and-package-stage.yml

@@ -1,4 +1,11 @@
+parameters:
+- name: dockerTag
+  type: string
+  default: nightly
+
 stages:
+  # If this stage name is changed, the value of builtDockerTag in the deploy
+  # stage needs to be updated.
   - stage: TestAndPackage
     jobs:
       - template: ../jobs/standard-tests-jobs.yml