steps:
- checkout: self
  fetchDepth: 5

- script: echo "##vso[task.setvariable variable=diffTarget]HEAD~1"
  displayName: Set default diff target

- script: |
    git fetch -q origin $(System.PullRequest.TargetBranch)
    echo "##vso[task.setvariable variable=diffTarget]HEAD \$(git merge-base HEAD FETCH_HEAD)"
  displayName: Fetch comparison tree
  condition: and(succeeded(), variables['System.PullRequest.TargetBranch'])

- script: |
   if ! git diff --name-only $(diffTarget) | grep -qvE '(\.rst$|^Doc|^Misc)'
   then
     echo "Only docs were updated: tests.run=false"
     echo "##vso[task.setvariable variable=run;isOutput=true]false"
   else
     echo "Code was updated: tests.run=true"
     echo "##vso[task.setvariable variable=run;isOutput=true]true"
   fi
  displayName: Detect source changes
  name: tests