temp local copy of userfunc

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

util/userfunc/doc.go

@@ -0,0 +1,22 @@
+// Package userfunc implements a HCL extension that allows user-defined
+// functions in HCL configuration.
+//
+// Using this extension requires some integration effort on the part of the
+// calling application, to pass any declared functions into a HCL evaluation
+// context after processing.
+//
+// The function declaration syntax looks like this:
+//
+//     function "foo" {
+//       params = ["name"]
+//       result = "Hello, ${name}!"
+//     }
+//
+// When a user-defined function is called, the expression given for the "result"
+// attribute is evaluated in an isolated evaluation context that defines variables
+// named after the given parameter names.
+//
+// The block name "function" may be overridden by the calling application, if
+// that default name conflicts with an existing block or attribute name in
+// the application.
+package userfunc