Script to provide TF_VARs from yaml

Semi generic script that reads a YAML tree and creates a bash
script to export the data as variables. They are prefixed
with *TF_VAR_* to be able to read them directly in Terraform.

concourse/scripts/extract_tf_vars_from_yaml.rb

@@ -0,0 +1,30 @@
+#!/usr/bin/env ruby
+#
+# Converts a YAML to a bunch of bash variable assignations.
+# - It will concatenate the key tree using '_' until it finds a basic value
+# - for lists, if the element is a hash and has a key 'name', uses that as
+#   a node name, if not, uses the index.
+
+require 'yaml'
+
+def process_yaml(yaml_tree, prefix_chain)
+  case yaml_tree
+  when Hash
+    yaml_tree.each { |k,v|
+      process_yaml(v, prefix_chain + [k])
+    }
+  when Array
+    yaml_tree.each_with_index { |v,i|
+      if v.instance_of? Hash and v['name']
+        name = v['name']
+      else
+        name = i
+      end
+      process_yaml(v, prefix_chain + [name])
+    }
+  else
+    puts "#{prefix_chain.join('_')}='#{yaml_tree}'"
+  end
+end
+
+process_yaml(YAML.load($stdin), ["export TF_VAR"])