Use SourceBranchName

azure-pipelines.yml

@@ -22,7 +22,7 @@ variables:
     _OfficialBuildIdArgs: /p:OfficialBuildId=$(Build.BuildNumber) 
       /p:ManifestTeamProject=AspNet
       /p:ManifestTeamName=AspNetCore-Tooling
-      /p:ManifestBuildBranch=$(Build.SourceBranch)
+      /p:ManifestBuildBranch=$(Build.SourceBranchName)
       /p:ManifestBuildNumber=$(Build.BuildNumber)
       /p:ManifestPublishUrl=https://vsdrop.corp.microsoft.com/file/v1/Products/AspNet/AspNetCore-Tooling/$(Build.SourceBranch)/$(Build.BuildNumber)
     _PublishArgs: /p:DotNetPublishBlobFeedKey=$(dotnetfeed-storage-access-key-1)