Scan files for unique guids. Generate replacements. Replace each guid in all files, committing between each guid.

gistfile1.ps1

param (
       [string] $path
      )

$oldPath = $pwd

cd (Resolve-Path $path)

$files = grep -rIlE "[0-9a-fA-F]\{8\}-[0-9a-fA-F]\{4\}-[0-9a-fA-F]\{4\}-[0-9a-fA-F]\{4\}-[0-9a-fA-F]\{12\}" * |
                  ? { !$_.Contains('.min.js') } | 
                  ? { !$_.Contains('tiny_mce') } | 
                  ? { !$_.Contains('jquery') }

$spFiles = $files |
                  ? { $_.EndsWith('FieldRegistry.cs') -or $_.EndsWith('Elements.xml') }


$guids = $spFiles | 
                  % { 
                          Get-Content $_ | % {
                                  $guidPattern = "[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}"
                                  $_ | 
                                      Select-String -pattern "$guidPattern" -AllMatches | 
                                      Select-Object -ExpandProperty Matches | 
                                      ? {$_.Value.ToString() -ne [System.Guid]::Empty.ToString()} |
                                      % {Write-Output $_.Value.ToLower()}
                          }
                  } | 
                  Select-Object -Unique | 
                  % { 
                    New-Object System.Object |
                    Add-Member -type NoteProperty -name 'Original' -value $_ -PassThru |
                    Add-Member -type NoteProperty -name 'Replacement' -value ([System.Guid]::NewGuid().ToString()) -PassThru |
                    Write-Output
                  }

$guids | % {
        $guid = $_
        $files | 
                % {
                  (Get-Content $_) | %{ $_ -replace $guid.Original, $guid.Replacement } | Set-Content $_
                }

        git commit -am ("Automated commit for guid replacement - " + $_.Original.ToString().ToUpper() + " -> " + $_.Replacement.ToString().ToUpper()) 
}

cd $oldPath