## Q:Test20181217SU_1385185.ps1
$Base = 'C:Test'
$ArchiveFolder = $Env:tmp

function Archive-Tree {
    $File = "{0}Tree_{1:yyyyMMddHHmmss}.CliXML" -f $ArchiveFolder,[datetime]::Now
    Get-ChildItem -Path $Base -Recurse | Export-Clixml $File
    $File
}

## ----- get most recent file Tree_*.clixml
$File = Get-ChildItem "$($Env:tmp)Tree_*.Clixml" | Select-Object -Last 1
if ($File){
    $Old = Import-Clixml $File
    $New = Import-Clixml (Archive-Tree)
    Compare-Object -Ref $Old -Dif $New -Property FullName,
            Length,LastWriteTime,CreationTime,LastAccessTime |
        Sort-Object FullName,SideIndicator | Format-Table -AutoSize
} else {
    $File = (Archive-Tree)
    "No saved tree, now created as {0}" -f $File
}

FullName              Length LastWriteTime       CreationTime        LastAccessTime      SideIndicator
--------              ------ -------------       ------------        --------------      -------------
C:testc_test.clixml 982258 2018-12-17 12:59:27 2018-12-17 12:59:24 2018-12-17 12:59:24 =>
C:testc_test.clixml      0 2018-12-17 12:59:24 2018-12-17 12:59:24 2018-12-17 12:59:24 <=
C:Testfoo.baz         1164 2018-12-17 13:55:05 2018-12-17 13:55:21 2018-12-17 13:55:21 =>