make the commit an environment variable to reuse in any stage

Jenkinsfile.cd

@@ -11,6 +11,10 @@ def shouldBail() {
 pipeline {
   agent any
 
+  environment {
+    commit = ''
+  }
+
   parameters {
       booleanParam(name: 'SKIP_BUILD', defaultValue: false, description: 'Set to true to skip the stage')
       booleanParam(name: 'SKIP_DEPLOY', defaultValue: false, description: 'Set to true to skip the stage')
@@ -23,6 +27,14 @@ pipeline {
       }
     }
 
+    stage('Set Commit') {
+      steps {
+        script {
+          env.commit = sh(returnStdout: true, script: "git rev-parse HEAD").trim()
+        }
+      }
+    }
+
     stage('Build new AMI') {
 
       when {
@@ -33,23 +45,20 @@ pipeline {
       }
 
       steps {
-        script {
-          commit = sh(returnStdout: true, script: "git rev-parse HEAD").trim()
-        }
-
         retry(3){
           build job: "builds/${params.app}", parameters: [
             booleanParam(name: 'release', value: false),
             booleanParam(name: 'notify_slack', value: true),
             stringParam(name: 'slack_channel', value: "${params.slack_channel}"),
-            stringParam(name: 'ref', value: commit),
+            stringParam(name: 'ref', value: env.commit),
             booleanParam(name: 'force_rebuild', value: true)
           ], wait: true
         }
       }
     }
 
     stage('Deploy to STAGING') {
+
       when {
         allOf {
           expression { return !params.SKIP_DEPLOY }
@@ -61,7 +70,7 @@ pipeline {
         build job: "deploys/${params.app}-vagov-staging", parameters: [
           stringParam(name: 'app', value: params.app),
           booleanParam(name: 'notify_slack', value: true),
-          stringParam(name: 'ref', value: commit),
+          stringParam(name: 'ref', value: env.commit),
           booleanParam(name: 'migration_status', value: false)
         ] , wait: false
       }