param(
    [Parameter(Mandatory=$true)]
    [string]
    $PRUrl,

    [switch]
    $PassThru
)

enum DiffState {
    None
    FileInfo
    DiffContent
}

[DiffState]$state = [DiffState]::None
$Log = @{}

$diffFile = Join-Path -Path $PSScriptRoot -ChildPath "diff.txt"
if (Test-Path -Path $diffFile) { Remove-Item -Path $diffFile -Force -ErrorAction Stop }

##
## .diff and .patch can be append in the end to get some raw content
##
$PRUrl += ".diff"
Invoke-WebRequest -Uri $PRUrl -OutFile $diffFile

$Script:ScanResult = $null
switch -Wildcard -File $diffFile
{
    "diff --git *"
        {
            $state = [DiffState]::FileInfo
            $fileName = ($_ -split " ")[-1].Substring(2)

            if ($Script:ScanResult -ne $null -and 
                $Script:ScanResult["OriginalStrs"].Count -ne $Script:ScanResult["NewStrs"].Count)
            {
                throw "$($Script:ScanResult['FileName']) contains mismatched + and -"
            }
            
            if ($Log.ContainsKey($fileName)) 
            {
                throw "$fileName appeared twice in diff file. Something is wrong"
            }

            $Script:ScanResult = @{ FileName = $fileName; OriginalStrs = @(); NewStrs = @() }
            $Log[$fileName] = $Script:ScanResult
        }

    "@@ * @@ *"
        {
            $state = [DiffState]::DiffContent
        }

    "-*"
        {
            if ($state -eq [DiffState]::DiffContent)
            {
                $old = $_.Substring(1)
                if (![string]::IsNullOrWhiteSpace($old))
                {
                    $Script:ScanResult["OriginalStrs"] += $old
                }
            }
        }

    "+*"
        {
            if ($state -eq [DiffState]::DiffContent)
            {
                $new = $_.Substring(1)
                if (![string]::IsNullOrWhiteSpace($new))
                {
                    $Script:ScanResult["NewStrs"] += $new
                }
            }
        }
}


Write-Host -Object "$($Log.Count) files involved in this PR`n"

foreach ($result in $Log.Values)
{
    $newStrs = $result["NewStrs"]
    $originalStrs = $result["OriginalStrs"]

    for ($i = 0; $i -lt $originalStrs.Length; $i++)
    {
        $oldString = $originalStrs[$i]
        $newString = $newStrs[$i]

        $xOldString = $oldString.Trim()
        $xNewString = $newString.TrimStart()

        $failed = $false
        if ($xOldString.StartsWith("}"))
        {
            ## Attempt 1 - }//blah => }
            $sub = $xOldString.Substring(1).Trim()
            $failed = !$sub.StartsWith("//")
            $xOldString = "}"
        }
        elseif ($xOldString.StartsWith("//"))
        {
            ## Attempt 2 - //var => // var
            $xOldString = "// " + $xOldString.Substring(2)
        }
        else
        {
            ## Attempt 3 - //var => // var
            $commentIndex = $xOldString.IndexOf("//")
            $firstHalf = $xOldString.Substring(0, $commentIndex)
            $lastHalf = "// " + $xOldString.Substring($commentIndex + 2)
            $xOldString = $firstHalf + $lastHalf
        }

        if ($failed -or $xOldString -cne $xNewString)
        {
            Write-Host @"
$($result['FileName']) - mismatch
Old: $oldString
New: $newString

"@
        }
    }
}

if ($PassThru) { return $Log }

PS:298> .\CheckAddSpace-8576.ps1 -PRUrl https://github.com/PowerShell/PowerShell/pull/8576
296 files involved in this PR

src/Microsoft.PowerShell.Commands.Management/commands/management/GetComputerInfoCommand.cs - mismatch
Old:         public string CsName { get; internal set; } //TODO: get rid of this? Is this about CIM rather than about the computer?
New:         public string CsName { get; internal set; }

src/Microsoft.PowerShell.CoreCLR.Eventing/DotNetCode/Eventing/Reader/ProviderMetadataCachedInformation.cs - mismatch
Old: }
New: }

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //sbCerts.Append(childnode.LocalName);
New:                     //        // sbCerts.Append(childnode.LocalName);

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //sbCerts.Append(WSManStringLiterals.Equalto);
New:                     //        // sbCerts.Append(WSManStringLiterals.Equalto);

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //sbCerts.Append(childnode.InnerText);
New:                     //        // sbCerts.Append(childnode.InnerText);

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //keys[0] = childnode.LocalName + WSManStringLiterals.Equalto + childnode.InnerText;
New:                     //        // keys[0] = childnode.LocalName + WSManStringLiterals.Equalto + childnode.InnerText;

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //sbCerts.Append(childnode.LocalName);
New:                     //        // sbCerts.Append(childnode.LocalName);

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //sbCerts.Append(WSManStringLiterals.Equalto);
New:                     //        // sbCerts.Append(WSManStringLiterals.Equalto);

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //sbCerts.Append(childnode.InnerText);
New:                     //        // sbCerts.Append(childnode.InnerText);

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //keys[1] = childnode.LocalName + WSManStringLiterals.Equalto + childnode.InnerText;
New:                     //        // keys[1] = childnode.LocalName + WSManStringLiterals.Equalto + childnode.InnerText;

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //sbCerts.Append(childnode.LocalName);
New:                     //        // sbCerts.Append(childnode.LocalName);

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //sbCerts.Append(WSManStringLiterals.Equalto);
New:                     //        // sbCerts.Append(WSManStringLiterals.Equalto);

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //sbCerts.Append(childnode.InnerText);
New:                     //        // sbCerts.Append(childnode.InnerText);

src/Microsoft.WSMan.Management/ConfigProvider.cs - mismatch
Old:                     //        //keys[2] = childnode.LocalName + WSManStringLiterals.Equalto + childnode.InnerText;
New:                     //        // keys[2] = childnode.LocalName + WSManStringLiterals.Equalto + childnode.InnerText;

src/System.Management.Automation/engine/parser/Parser.cs - mismatch
Old:                 //    //Diagnostics.Assert(token.Text.Equals("${}", StringComparison.OrdinalIgnoreCase),
New:                 //    // Diagnostics.Assert(token.Text.Equals("${}", StringComparison.OrdinalIgnoreCase),

src/System.Management.Automation/engine/ExecutionContext.cs - mismatch
Old:             // Reset the command origin for script commands... //BUGBUG - dotting can get around command origin checks???
New:             // Reset the command origin for script commands... // BUGBUG - dotting can get around command origin checks???

src/System.Management.Automation/engine/remoting/client/Job.cs - mismatch
Old:             //                //ISSUE: Change this code to look in to child jobs for exception
New:             //                // ISSUE: Change this code to look in to child jobs for exception

src/Microsoft.PowerShell.CoreCLR.Eventing/DotNetCode/Eventing/UnsafeNativeMethods.cs - mismatch
Old:             EvtQueryNames = 0,   //String;   //Variant will be array of EvtVarTypeString
New:             EvtQueryNames = 0,   // String;   // Variant will be array of EvtVarTypeString

src/Microsoft.PowerShell.CoreCLR.Eventing/DotNetCode/Eventing/UnsafeNativeMethods.cs - mismatch
Old:             EvtQueryStatuses = 1 //UInt32;   //Variant will be Array of EvtVarTypeUInt32
New:             EvtQueryStatuses = 1 // UInt32;   // Variant will be Array of EvtVarTypeUInt32