A group name should not be a valid target.

[xunker]

Currently, if I set up my target map as

activate :target do |t|
  t.build_targets = {
    "phonegap" => {
      :includes => %w[android ios]
    }
  }
end

I could do this

MIDDLEMAN_BUILD_TARGET=phonegap middleman build

And it would be accepted but would not do what you expected. Need to throw an exception or error if the given target is actually a group.