I try to create Azure DevOps pipeline and i want to append commit message to each pipeline run that is not executed from tags.

Start of my code looks like this:

name: $(Build.SourceBranchName)
appendCommitMessageToRunName: false

And that does a trick:

The problem is, that when its executed on tag i dont want to append commit message but any other branch, i want to. I try to code it like that:

name: $(Build.SourceBranchName)

variables:
- name: appendCommitMessageToRunName
  ${{ if startsWith(variables['Build.SourceBranch'], 'refs/tags/') }}:
    value: false
  ${{ if not(startsWith(variables['Build.SourceBranch'], 'refs/tags/')) }}:
    value: true

But unfortunately, it does not work.

So how to append commit message based on source branch name?