Templating Functions & HCL Variables for Artifacts, Deploys

[mitchellh]

This introduces two major features (related):

• A set of a template-prefixed HCL functions that template files or directories with the currently available HCL variables.
• Artifact, deploy HCL variables for registry, deploy, and release stanzas. You can use this to reference information about the result of the prior operation.

This PR temporarily disables auth checks completely. We will add these again at runtime in a future PR, prior to 0.2.0.

Depends on hashicorp/waypoint-plugin-sdk#5 and will update go.mod after merging that.

Example

app "web" {
  build {
    use "docker" {
      dockerfile = templatefile("${path.app}/Dockerfile.prod", {
        custom_var = "hello"
      })
    }

    registry {
      use "docker" {
        image = artifact.image
        tag = gitrefpretty()
      }
    }
  }
  
  # ...
}

[krantzinator]

Exciting 🎉

[evanphx]

This is a biggy! All looks good, though it's hard to follow some of the changes, like I wasn't sure why all the template functions don't take a basedir anymore? I must have missed something in the reading where that basedir is coming from now. Maybe it's that the base dir is being applied to path elsewhere now?