Compare all the files of the same name in two directories.

TortoiseDiffAllFiles.ps1

Get-ChildItem C:\dir\* | %{
    $file1 = "C:\dir\$($_.Name)"
    $file2 = "C:\dir\$($_.Name)"
    . 'C:\Program Files\TortoiseGit\bin\TortoiseGitMerge.exe' -mine $file1 -base $file2
    #it takes a few seconds to open gitmerge. If you don't include this sleep your computer will implode.
    Start-Sleep -Seconds 5
}