Add the deprecation warning and update docs

hcl2template/types.packer_config.go

@@ -5,6 +5,7 @@ package hcl2template
 
 import (
 	"fmt"
+	"log"
 	"sort"
 	"strings"
 
@@ -112,6 +113,7 @@ func (cfg *PackerConfig) EvalContext(ctx BlockContext, variables map[string]cty.
 			packerAccessor: cty.ObjectVal(map[string]cty.Value{
 				"version":            cty.StringVal(cfg.CorePackerVersionString),
 				"iterationID":        cty.UnknownVal(cty.String),
+				"versionFingerprint": cty.UnknownVal(cty.String),
 			}),
 			pathVariablesAccessor: cty.ObjectVal(map[string]cty.Value{
 				"cwd":  cty.StringVal(strings.ReplaceAll(cfg.Cwd, `\`, `/`)),
@@ -122,6 +124,8 @@ func (cfg *PackerConfig) EvalContext(ctx BlockContext, variables map[string]cty.
 
 	iterID, ok := cfg.HCPVars["iterationID"]
 	if ok {
+		log.Printf("[WARN] Deprecation: Contextual Variable `iterationID` has been deprecated packer context. " +
+			"Please use `versionFingerprint` variable instead.")
 		ectx.Variables[packerAccessor] = cty.ObjectVal(map[string]cty.Value{
 			"version":     cty.StringVal(cfg.CorePackerVersionString),
 			"iterationID": iterID,

website/content/docs/templates/hcl_templates/contextual-variables.mdx

@@ -132,6 +132,8 @@ parenthesis may through off your shell escaping otherwise.
 
 # HCP Packer Iteration ID
 
+~> **Note**: Deprecation: Contextual Variable `iterationID` has been deprecated packer context. Please use `versionFingerprint` variable instead.
+
 If your build is pushing metadata to the HCP Packer registry, this variable is
 set to the value of the Iteration ID associated with this run.
 
@@ -145,6 +147,22 @@ source "amazon-ebs" "cannonical-ubuntu-server" {
 }
 ```
 
+# HCP Packer Version Fingerprint
+
+If your build is pushing metadata to the HCP Packer registry, this variable is
+set to the value of the Version Fingerprint associated with this run.
+
+```hcl
+source "amazon-ebs" "cannonical-ubuntu-server" {
+  ami_name         = "packer-example"
+  // ...
+  run_volume_tags = {
+    hcp_version_fingerprint = packer.versionFingerprint
+  }
+}
+```
+
+
 ```shell-session
 ==> vanilla.amazon-ebs.cannonical-ubuntu-server: Adding tags to source instance
     vanilla.amazon-ebs.cannonical-ubuntu-server: Adding tag: "Name": "Packer Builder"
@@ -158,6 +176,8 @@ You can also add this value to post-processors, for example to add to a manifest
     output     = "manifest.json"
     strip_path = true
     custom_data = {
+      version_fingerprint = "${packer.versionFingerprint}"
+      // `packer.iterationID` has been deprecated.
       iteration = "${packer.iterationID}"
     }
   }