Sync eng/common directory with azure-sdk-tools for PR 1088 (Azure#15952)

Sync eng/common directory with azure-sdk-tools for PR Azure/azure-sdk-tools#1088
 See [eng/common workflow](https://github.com/Azure/azure-sdk-tools/blob/master/eng/common/README.md#workflow)

eng/common/scripts/Delete-RemoteBranches.ps1

@@ -0,0 +1,44 @@
+param(
+  $RepoOwner,
+  $RepoName,
+  $BranchPrefix,
+  $AuthToken
+)
+
+. "${PSScriptRoot}\common.ps1"
+
+LogDebug "Operating on Repo [ $RepoName ]"
+try{
+  $branches = (List-References -RepoOwner $RepoOwner -RepoName $RepoName -Ref "heads/$BranchPrefix").ref
+}
+catch {
+  LogError "List-References failed with exception:`n$_"
+  exit 1
+}
+
+foreach ($branch in $branches)
+{
+  try {
+    $branchName = $branch.Replace("refs/heads/","")
+    $head = "${RepoOwner}/${RepoName}:${branchName}"
+    LogDebug "Operating on branch [ $branchName ]"
+    $pullRequests = List-PullRequests -RepoOwner $RepoOwner -RepoName $RepoName -head $head
+  }
+  catch
+  {
+    LogError "List-PullRequests failed with exception:`n$_"
+    exit 1
+  }
+
+  if ($pullRequests.Count -eq 0)
+  {
+    LogDebug "Branch [ $branchName ] in repo [ $RepoName ] has no associated Pull Request. Deleting Branch"
+    try{
+      Delete-References -RepoOwner $RepoOwner -RepoName $RepoName -Ref ($branch.Remove(0,5)) -AuthToken $AuthToken
+    }
+    catch {
+      LogError "Delete-References failed with exception:`n$_"
+      exit 1
+    }
+  }
+}

eng/common/scripts/Invoke-GitHubAPI.ps1

@@ -47,6 +47,24 @@ function Invoke-GitHubAPIPatch {
   return $resp
 }
 
+function Invoke-GitHubAPIDelete {
+  param (
+    [Parameter(Mandatory = $true)]
+    $apiURI,
+    [Parameter(Mandatory = $true)]
+    $token
+  )
+
+  $resp = Invoke-RestMethod `
+    -Method DELETE `
+    -Uri $apiURI `
+    -Headers (Get-GitHubHeaders -token $token) `
+    -MaximumRetryCount 3
+
+  return $resp
+}
+
+
 function Invoke-GitHubAPIGet {
   param (
     [Parameter(Mandatory = $true)]
@@ -105,6 +123,27 @@ function List-PullRequests {
   return Invoke-GitHubAPIGet -apiURI $uri
 }
 
+# 
+<#
+.PARAMETER Ref
+Ref to search for
+Pass 'heads/<branchame> ,tags/<tag name>, or nothing
+#>
+function List-References {
+  param (
+    [Parameter(Mandatory = $true)]
+    $RepoOwner,
+    [Parameter(Mandatory = $true)]
+    $RepoName,
+    $Ref
+  )
+
+  $uri = "$GithubAPIBaseURI/$RepoOwner/$RepoName/git/matching-refs/"
+  if ($Ref) { $uri += "$Ref" }
+
+  return Invoke-GitHubAPIGet -apiURI $uri
+}
+
 function Add-IssueComment {
   param (
     [Parameter(Mandatory = $true)]
@@ -229,4 +268,27 @@ function Update-Issue {
   }
 
   return Invoke-GitHubAPIPatch -apiURI $uri -body $parameters -token $AuthToken
+}
+
+function Delete-References {
+  param (
+    [Parameter(Mandatory = $true)]
+    $RepoOwner,
+    [Parameter(Mandatory = $true)]
+    $RepoName,
+    [ValidateNotNullOrEmpty()]
+    [Parameter(Mandatory = $true)]
+    $Ref,
+    [Parameter(Mandatory = $true)]
+    $AuthToken
+  )
+
+  if ($Ref.Trim().Length -eq 0)
+  {
+    throw "You must supply a valid 'Ref' Parameter to 'Delete-Reference'."
+  }
+
+  $uri = "$GithubAPIBaseURI/$RepoOwner/$RepoName/git/refs/$Ref"
+
+  return Invoke-GitHubAPIDelete -apiURI $uri -token $AuthToken
 }