feat: allow configuration of initial terraform version in tf_cloudbui…

…ld_builder (#189)

* allow configuration of default terraform version in tf_cloudbuild_builder

* fix split function parameter order

modules/tf_cloudbuild_builder/README.md

@@ -43,6 +43,7 @@ This module creates:
 | gar\_repo\_name | Name of the Google Artifact Repository where the Terraform builder images are stored. | `string` | `"tf-runners"` | no |
 | image\_name | Name of the image for the Terraform builder. | `string` | `"terraform"` | no |
 | project\_id | GCP project for Cloud Build trigger,workflow and scheduler. | `string` | n/a | yes |
+| terraform\_version | The initial terraform version in semantic version format. | `string` | `"1.1.0"` | no |
 | trigger\_name | Name of the Cloud Build trigger building the Terraform builder. | `string` | `"tf-cloud-builder-build"` | no |
 | workflow\_name | Name of the workflow managing builds. | `string` | `"terraform-runner-workflow"` | no |
 | workflow\_region | The region of the workflow. | `string` | `"us-central1"` | no |

modules/tf_cloudbuild_builder/cb.tf

@@ -18,11 +18,16 @@ locals {
   gar_uri             = "${var.gar_repo_location}-docker.pkg.dev/${var.project_id}/${local.gar_name}/${var.image_name}"
   cloudbuild_sa       = coalesce(var.cloudbuild_sa, google_service_account.cb_sa[0].id)
   cloudbuild_sa_email = element(split("/", local.cloudbuild_sa), length(split("/", local.cloudbuild_sa)) - 1)
+  tf_version_parts    = split(".", var.terraform_version)
+  tf_full_version     = var.terraform_version
+  tf_minor_version    = "${local.tf_version_parts[0]}.${local.tf_version_parts[1]}"
+  tf_major_version    = local.tf_version_parts[0]
+
   # substitutions available in the CB trigger
   tags_subst = {
-    "_TERRAFORM_FULL_VERSION"  = "1.1.0",
-    "_TERRAFORM_MINOR_VERSION" = "1.1",
-    "_TERRAFORM_MAJOR_VERSION" = "1",
+    "_TERRAFORM_FULL_VERSION"  = "${local.tf_full_version}",
+    "_TERRAFORM_MINOR_VERSION" = "${local.tf_minor_version}",
+    "_TERRAFORM_MAJOR_VERSION" = "${local.tf_major_version}",
   }
   img_tags_subst = [for tag in keys(local.tags_subst) : "${local.gar_uri}:v$${${tag}}"]
 

modules/tf_cloudbuild_builder/variables.tf

@@ -67,6 +67,12 @@ variable "gar_repo_location" {
   default     = "us"
 }
 
+variable "terraform_version" {
+  description = "The initial terraform version in semantic version format."
+  type        = string
+  default     = "1.1.0"
+}
+
 variable "image_name" {
   description = "Name of the image for the Terraform builder."
   type        = string