take all files in $from and put them in the same place under $to, replacing any matched files

merge.ps1

$from = $from | gi
$to = ($to | gi).FullName

$from `
| Get-ChildItem -File -Recurse `
| &{
	Begin {
		$from = '^' + [Regex]::Escape($from.FullName)
	}
	Process {
		$_ `
		| Move-Item `
			-Force `
			-Destination (
				New-Item `
					-Force `
					-Type Directory `
					-Path ($_.Directory.FullName -replace $from,$to)
			)
	}
}