Could not find remote branch: refs/heads/master in YAML pipeline about vststasks

[Good-man]

I figured it out. Not only do you need persistCredentials: true (I think):

  steps:
  - checkout: self 
    persistCredentials: true

But you also need env: and SYSTEM_ACCESSTOKEN: $(System.AccessToken) as shown:

  - task: GitflowBranchGate@1
    inputs:
      repository: '$(Build.Repository.Name)'
      masterBranch: 'master'
      developBranch: 'develop'
      hotfixBranches: 'hotfix/*'
      releaseBranches: 'release/*'
      featureBranches: 'feature/*'
      hotfixBranchLimit: '1'
      hotfixBranchDaysLimit: '10'
      releaseBranchLimit: '1'
      releaseBranchDaysLimit: '10'
      featureBranchLimit: '50'
      featureBranchDaysLimit: '45'
      featureBranchesMustNotBeBehindMaster: false
      authenticationType: 'OAuthToken'
    env:
      SYSTEM_ACCESSTOKEN: $(System.AccessToken)