Attempting to grab source branch name

azure-pipelines.yml

@@ -142,7 +142,7 @@ stages:
             tags: $(imageTag)
             arguments: '--no-cache --pull'
         - bash: |
-              branch_name=$(git name-rev --name-only --refs="refs/remotes/origin/*" HEAD^1 | sed 's/~.*//')  # Had to do it this way because Build.SourceBranchName is always 'merge' on PR
+              branch_name=$(System.PullRequest.SourceBranch)
               echo "Retrieved branch name: '$branch_name'"
               jira_card_number="${branch_name##*/}"           # Grab everything after last '/'
               # Create container for jira writeback