Have default value for helper function

eng/common/pipelines/templates/steps/credscan.yml

@@ -11,7 +11,7 @@ steps:
       # Add config to disable the quote and encoding on file name. 
       # Ref: https://github.com/msysgit/msysgit/wiki/Git-for-Windows-Unicode-Support#disable-quoted-file-names
       # Ref: https://github.com/msysgit/msysgit/wiki/Git-for-Windows-Unicode-Support#disable-commit-message-transcoding
-      $changedFiles = & 'eng/common/scripts/get-diff-changes-from-PR.ps1'
+      $changedFiles = & 'eng/common/scripts/get-diff-changes.ps1'
       $changedFiles | ForEach-Object { Add-Content -Path "${{ parameters.SourceDirectory }}/credscan.tsv" -Value "${{ parameters.SourceDirectory }}/$_"}
     }
     else {

eng/common/pipelines/templates/steps/eng-common-workflow-enforcer.yml

@@ -12,7 +12,7 @@ steps:
 
         if ((!"$(System.PullRequest.SourceBranch)".StartsWith("sync-eng/common")) -and $targetBranch -eq $defaultBranch)
         {
-          $filesInCommonDir  = & 'eng/common/scripts/get-diff-changes-from-PR.ps1' -DiffPath 'eng/common/*'
+          $filesInCommonDir  = & 'eng/common/scripts/get-diff-changes.ps1' -DiffPath 'eng/common/*'
           if (($LASTEXITCODE -eq 0) -and ($filesInCommonDir.Count -gt 0))
           {
             Write-Host "##vso[task.LogIssue type=error;]Changes to files under 'eng/common' directory should not be made in this Repo`n${filesInCommonDir}"

eng/common/scripts/get-diff-changes-from-PR.ps1

@@ -1,39 +1,19 @@
-<#
-  .SYNOPSIS
-  Returns git diff changes in pull request.
-  .DESCRIPTION
-  The script is to return diff changes in pull request.
-  .PARAMETER SourceCommittish
-  The branch committish PR merges from.
-  Definition of committish: https://git-scm.com/docs/gitglossary#Documentation/gitglossary.txt-aiddefcommit-ishacommit-ishalsocommittish
-  .PARAMETER TargetCommittish
-  The branch committish PR targets to merge into.
-  .PARAMETER DiffPath
-  The files which git diff to scan against. Support regex match. E.g. "eng/common/*", "*.md"
-  .PARAMETER DiffFilterType
-  The filter type A(a)dd, D(d)elete, R(r)ename, U(u)pate. 
-  E.g. 'ad' means filter out the newly added file and deleted file 
-  E.g. '' means no filter on file mode.
-#>
-[CmdletBinding()]
-param (
-  [string] $SourceCommittish = "${env:BUILD_SOURCEVERSION}",
-  [string] $TargetCommittish = ("origin/${env:SYSTEM_PULLREQUEST_TARGETBRANCH}" -replace "refs/heads/"),
-  [string] $DiffPath = "",
-  [string] $DiffFilterType = 'd'
-)
 
-#Set-StrictMode -Version 3
-
-function Get-PullRequest-Diff-Changes($SourceCommittish, $TargetCommittish, $DiffPath, $DiffFilterType) {
+function Get-PullRequest-Diff-Changes {
+  param (
+    [string]$SourceCommittish= "${env:BUILD_SOURCEVERSION}",
+    [string]$TargetCommittish = ("origin/${env:SYSTEM_PULLREQUEST_TARGETBRANCH}" -replace "refs/heads/"),
+    [string]$DiffPath,
+    [string]$DiffFilterType = "d"
+  )
   # If ${env:SYSTEM_PULLREQUEST_TARGETBRANCH} is empty, then return empty.
   if ($TargetCommittish -eq "origin/") {
     Write-Host "There is no target branch passed in. "
     return ""
   }
 
   # Git PR diff: https://docs.github.com/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-comparing-branches-in-pull-requests#three-dot-and-two-dot-git-diff-comparisons
-  $command = "git -c core.quotepath=off -c i18n.logoutputencoding=utf-8 diff `"$TargetCommittish...HEAD`" --name-only --diff-filter=$DiffFilterType"
+  $command = "git -c core.quotepath=off -c i18n.logoutputencoding=utf-8 diff `"$TargetCommittish...$SourceCommittish`" --name-only --diff-filter=$DiffFilterType"
   if ($DiffPath) {
   $command = $command + " -- `'$DiffPath`'"
   }
@@ -50,8 +30,3 @@ function Get-PullRequest-Diff-Changes($SourceCommittish, $TargetCommittish, $Dif
   }
   return $changedFiles
 }
-
-return Get-PullRequest-Diff-Changes -SourceCommittish $SourceCommittish `
-        -TargetCommittish $TargetCommittish `
-        -DiffPath $DiffPath `
-        -DiffFilterType $DiffFilterType

eng/common/scripts/get-markdown-files-from-changed-files.ps1

@@ -5,6 +5,6 @@ param (
   [string] $targetBranch = ("origin/${env:SYSTEM_PULLREQUEST_TARGETBRANCH}" -replace "/refs/heads/")
 )
 
-. (Join-Path $PSScriptRoot get-diff-changes-from-PR.ps1)
+. (Join-Path $PSScriptRoot common.ps1)
 
 return Get-PullRequest-Diff-Changes -TargetCommittish $targetBranch -DiffPath '*.md'