Use updated environment variable for branch build scan metadata

Author: mark-vieira

gradle/build-scan.gradle

@@ -52,6 +52,8 @@ buildScan {
     link 'CI Build', buildUrl
     link 'GCP Upload', "https://console.cloud.google.com/storage/browser/_details/elasticsearch-ci-artifacts/jobs/${URLEncoder.encode(jobName, "UTF-8")}/build/${buildNumber}.tar.bz2"
     value 'Job Number', buildNumber
+    value 'Git Branch', System.getenv('JOB_BRANCH')
+    tag System.getenv('JOB_BRANCH')
 
     System.getenv().getOrDefault('NODE_LABELS', '').split(' ').each {
       value 'Jenkins Worker Label', it
@@ -61,18 +63,11 @@ buildScan {
     def isPrBuild = System.getenv('ROOT_BUILD_CAUSE_GHPRBCAUSE') != null
     if (isPrBuild) {
       value 'Git Commit ID', System.getenv('ghprbActualCommit')
-      value 'Git Branch', System.getenv('ghprbTargetBranch')
-      tag System.getenv('ghprbTargetBranch')
       tag "pr/${System.getenv('ghprbPullId')}"
       tag 'pull-request'
       link 'Source', "https://github.com/elastic/elasticsearch/tree/${System.getenv('ghprbActualCommit')}"
       link 'Pull Request', System.getenv('ghprbPullLink')
     } else {
-      if (System.getenv('GIT_BRANCH')) {
-        def branch = System.getenv('GIT_BRANCH').split('/').last()
-        value 'Git Branch', branch
-        tag branch
-      }
       if (System.getenv('GIT_COMMIT')) {
         value 'Git Commit ID', System.getenv('GIT_COMMIT')
         link 'Source', "https://github.com/elastic/elasticsearch/tree/${System.getenv('GIT_COMMIT')}"