configuration-language

Is your feature request related to a problem? Please describe.
Currently, polymorphic types are instantiated as in a standard Hindley-Milner system, that is as soon as a variable is used. While this is customary in the Hindley-Milner type system, it's limiting in a type system with full polymorphism (à la System F) like Nickel, as it results in polymorphic types being instantiated without nec

Any Jsonnet value can be bound to an external variable, even functions, which are accessible anywhere in the config, or any file, using std.extVar("foo")

jsonnet --ext-str version="0.9" --ext-code dry-run=true ...

local build_image_version = std.extVar('version');
local dry_run = std.extVar('dry-run');
...
local run(name, commands) = {  
  name: name,  
  image