internal/relui: use workflow output with communications not merged

The workflow package requires all tasks to be referenced somehow, and
they weren't if the comms tasks were disabled.

For golang/go#53537.

Change-Id: Iafb60cb9a73d8e1583456cee3e9667150259338e
Reviewed-on: https://go-review.googlesource.com/c/build/+/416218
Reviewed-by: Dmitri Shuralyov <[email protected]>
Auto-Submit: Heschi Kreinick <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Heschi Kreinick <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: heschi

internal/relui/workflows.go

@@ -708,7 +708,7 @@ func addSingleReleaseWorkflow(
 
 	pushed := wd.Action("Push issues", milestone.PushIssues, milestones, nextVersion, kindVal, tagged)
 	versionPublished = wd.Task("Publish to website", build.publishArtifacts, nextVersion, signedAndTestedArtifacts, pushed)
-
+	wd.Output("Released version", versionPublished)
 	return versionPublished, nil
 }
 

internal/workflow/workflow.go

@@ -23,6 +23,8 @@
 // a value of any type and an error. The TaskContext can be used as a normal
 // Context, and also supports workflow features like unstructured logging.
 // A task only runs once all of its input Values and Dependencies are ready.
+// All task outputs must be used either as inputs to another task or as a
+// workflow Output.
 //
 // In addition to Tasks, a workflow can have Actions, which represent functions
 // that don't produce an output. Their Go function must only return an error,