Change the extension of a set of files in powershell (in this gist from .markdown to .md)

ChangeExtension.ps1

foreach ($itFile in ls *.markdown)
{
    if ($itFile -match '(.*)\.(\w+)')
    {
        Write-Host 'Renaming '  $itFile
        $destFile = $Matches[1] + '.md' 
        mv $itFile $destFile
    }
}