Azure pipeline to read files in a pull request

I'm trying to build a azure pipeline to lint R scripts in a pull request as one of the steps to allow pull requests to be approved and completed.

I can get the pipeline to run R and library everything I need, but I am struggling to find a way to access the R scripts changed in a pull request via the pipeline.

Any help would be greatly appreciated.

You can find changed files of PR with git commands. Add it to the PR validation build, as an example for PR to the master branch:

git diff --name-only --relative --diff-filter AMR origin/master -- . > $(Build.StagingDirectory)/repo_changes.txt

Here is the example to copy only changed files with PowerShell (PowerShell task)

$targetfolder = "$(Build.StagingDirectory)" + "/"

function CopyFiles{
    param( [string]$source )

    $target = $targetfolder + $source

    New-Item -Force $target
    copy-item $source $target -Force
}

$changes = git diff --name-only --relative --diff-filter AMR origin/master --name-only -- .

if ($changes -is [string]){ CopyFiles $changes }
else
{
    if ($changes -is [array])
    {       
        foreach ($change in $changes){ CopyFiles $change }
    }
}

The part of yaml file may be like that:

jobs:
- job: get_changed_files
  steps:  
   - task: PowerShell@2
     inputs:
       targetType: 'inline'
       script: |
         $targetfolder = "$(Build.StagingDirectory)" + "/"
         
         function CopyFiles{
             param( [string]$source )
         
             $target = $targetfolder + $source
         
             New-Item -Force $target
             copy-item $source $target -Force
         }
         
         $changes = git diff --name-only --relative --diff-filter AMR origin/master -- .
         
         if ($changes -is [string]){ CopyFiles $changes }
         else
         {
             if ($changes -is [array])
             {       
                 foreach ($change in $changes){ CopyFiles $change }
             }
         }
   - task: PublishBuildArtifacts@1
     inputs:
      pathToPublish: $(Build.StagingDirectory)
      artifactName: MyChangedFiles