Re-add get-codeowners.ps1 (#3088)

Co-authored-by: Chidozie Ononiwu <chononiw@microsoft.com>

eng/common/scripts/get-codeowners.ps1

@@ -0,0 +1,49 @@
+param (
+  $TargetDirectory, # should be in relative form from root of repo. EG: sdk/servicebus
+  $RootDirectory, # ideally $(Build.SourcesDirectory)
+  $VsoVariable = "" # target devops output variable
+)
+$target = $TargetDirectory.ToLower().Trim("/")
+$codeOwnersLocation = Join-Path $RootDirectory -ChildPath ".github/CODEOWNERS"
+$ownedFolders = @{}
+
+if (!(Test-Path $codeOwnersLocation)) {
+  Write-Host "Unable to find CODEOWNERS file in target directory $RootDirectory"
+  exit 1
+}
+
+$codeOwnersContent = Get-Content $codeOwnersLocation
+
+foreach ($contentLine in $codeOwnersContent) {
+  if (-not $contentLine.StartsWith("#") -and $contentLine){
+    $splitLine = $contentLine -split "\s+"
+    
+    # CODEOWNERS file can also have labels present after the owner aliases
+    # gh aliases start with @ in codeowners. don't pass on to API calls
+    $ownedFolders[$splitLine[0].ToLower().Trim("/")] = ($splitLine[1..$($splitLine.Length)] `
+      | ? { $_.StartsWith("@") } `
+      | % { return $_.substring(1) }) -join ","
+  }
+}
+
+$results = $ownedFolders[$target]
+
+if ($results) {
+  Write-Host "Found a folder $results to match $target"
+  
+  if ($VsoVariable) {
+    $alreadyPresent = [System.Environment]::GetEnvironmentVariable($VsoVariable)
+
+    if ($alreadyPresent) { 
+      $results += ",$alreadyPresent"
+    }
+    Write-Host "##vso[task.setvariable variable=$VsoVariable;]$results"
+  }
+
+  return $results
+}
+else {
+  Write-Host "Unable to match path $target in CODEOWNERS file located at $codeOwnersLocation."
+  Write-Host ($ownedFolders | ConvertTo-Json)
+  return ""
+}