We have a situation where we would like to include a variable file only if it is present, and not to include any other. Specifically we want the ability to optionally set variables per passed “git_branch” in a project. An example playbook:
There’s no other syntax so the blank file is fine.
Michael,
Cool. I’ve gone ahead and moved the blank file from the host_vars directory to elsewhere in order to dispel the confusion and speedup file lookups in that directory! 
Owe you for that motivation. Have been struggling to deliver an organizational structure that makes sense and is fully up to date w/ latest ansible 1.4… although am beginning to see the light!