PS - ReplaceFiles script

<#
.SYNOPSIS
Replacefiles copies from one directory to the other, optionally only replacing files that exist in the target directory
.DESCRIPTION
Replacefiles copies from one directory to the other, optionally only replacing files that exist in the target directory
.PARAMETER SourceDirectory
Location of new files \\SourceLocation
.PARAMETER TargetDirectory
Location of old files \\TargetLocation
.PARAMETER Filenames
Name of files to copy -Filenames fileone.ext, filetwo.ext, file3.ext
.PARAMETER AlwaysCopy
Replacefiles will also copy files that are not present in the target directory
.EXAMPLE
ReplaceFiles -source C:\Build\Executables -target \\SomewhereElse -filenames thisfile.exe, somefile.txt, thatfile.exe -AlwaysCopy
#>
[CmdletBinding()]
param (
[Parameter(Mandatory=$True)]
[Alias('source')]
[String]$SourceDirectory,
[Parameter(Mandatory=$True)]
[Alias('target')]
[String]$TargetDirectory,
[Parameter(Mandatory=$True)]
[String[]]$Filenames,
[switch]$AlwaysCopy
)

if (test-path $SourceDirectory)
{
  if (test-path $TargetDirectory)
  {
    Write-Verbose "Replace files in $TargetDirectory from $SourceDirectory"
    if ($alwayscopy)
    {
        Write-Verbose "and add files that are not already present."
    }

    foreach($file in $Filenames)
    {
        Write-Verbose $file
        $new = Join-Path $SourceDirectory $file
        $old = Join-Path $TargetDirectory $file
        $newtmp = $old + '.new'
        $tmp = $old + '.tmp'
        $tmpfile = $file + '.tmp'

        $cpy = $AlwaysCopy
        if (Test-Path $old)
        {
            $cpy = $True
        }

        if (-not (Test-Path $New))
        {
            Write-Host $new not found
            $cpy = $False
        }

        if ($cpy)
        {

            Write-Host "Copying $file"

            if (Test-Path $tmp)
            {
                Write-Verbose "Deleting $tmp"
                Remove-Item $tmp -Force -ErrorAction SilentlyContinue
            }

            if (Test-Path $newtmp)
            {
                Write-Verbose "Deleting $newtmp"
                Remove-Item $newtmp -Force -ErrorAction SilentlyContinue
            }

            Write-Verbose "Copying $new to $newtmp"
            Copy-Item $new -Destination $newtmp -Force

            if (Test-Path $old)
            {
                Write-Verbose "Renaming $file to $tmpfile"
                Rename-Item $old -NewName $tmpfile -Force
            }

            Write-Verbose "Renaming $newtmp to $file"
            Rename-Item $newtmp -NewName $file -Force

            if (Test-Path $tmp)
            {
                Write-Verbose "Deleting $tmp"
                Remove-Item $tmp -Force -ErrorAction SilentlyContinue
            }
        }
        else {
            Write-Verbose "Skipped $file"
        }
    }
    Write-Verbose "ReplaceFiles completed"
  }
  else {
    Write-Error "Target directory $TargetDirectory does not exists"
  }
} else {
  Write-Error "Source directory $SourceDirectory does not exists"
}