Added PR opening script (#3302)

* Added PR opening script

(cherry picked from commit 14662d2)

* Update open-pullrequest.ps1

open-pullrequest.ps1

@@ -0,0 +1,24 @@
+param(
+    [Parameter(Mandatory)]
+    [string]
+    $SourceBranch
+) 
+
+function Get-PullRequest() {
+    $prInfo = (gh api -X GET repos/:owner/:repo/pulls -F head=":owner:$SourceBranch" -f state=open -f base=master | ConvertFrom-Json)
+    return $prInfo.html_url
+}
+
+$openedPR = Get-PullRequest
+
+if ($openedPR.length -ne 0) {
+    throw "A PR from $SourceBranch to master already exists."
+}
+
+$buildUrl = "$env:SYSTEM_TEAMFOUNDATIONCOLLECTIONURI$env:SYSTEM_TEAMPROJECT/_build/results?buildId=$env:BUILD_BUILDID&_a=summary"
+$body = "This PR was auto-generated with [the localization pipeline build]($buildUrl)."
+
+gh pr create --head $SourceBranch --title 'Localization update' --body $body
+
+# Getting a link to the opened PR
+$env:PR_LINK = Get-PullRequest