Recursively diffs 2 directories (files and contents) using MD5 hashes - Includes validation for paths and optional summary export. Requires PowerShell 3.0 or later.

rdiff.ps1

#########################################################################
### USAGE: rdiff path/to/left,path/to/right [-s path/to/summary/dir]  ###
### ADD LOCATION OF THIS SCRIPT TO PATH                               ###
#########################################################################
[CmdletBinding()]
param (
  [parameter(HelpMessage="Stores the execution working directory.")]
  [string]$ExecutionDirectory=$PWD,

  [parameter(Position=0,HelpMessage="Compare two directories recursively for differences.")]
  [alias("c")]
  [string[]]$Compare,

  [parameter(HelpMessage="Export a summary to path.")]
  [alias("s")]
  [string]$ExportSummary
)

### FUNCTION DEFINITIONS ###

# SETS WORKING DIRECTORY FOR .NET #
function SetWorkDir($PathName, $TestPath) {
  $AbsPath = NormalizePath $PathName $TestPath
  Set-Location $AbsPath
  [System.IO.Directory]::SetCurrentDirectory($AbsPath)
}

# RESTORES THE EXECUTION WORKING DIRECTORY AND EXITS #
function SafeExit() {
  SetWorkDir /path/to/execution/directory $ExecutionDirectory
  Exit
}

function Print {
  [CmdletBinding()]
  param (
    [parameter(Mandatory=$TRUE,Position=0,HelpMessage="Message to print.")]
    [string]$Message,

    [parameter(HelpMessage="Specifies a success.")]
    [alias("s")]
    [switch]$SuccessFlag,

    [parameter(HelpMessage="Specifies a warning.")]
    [alias("w")]
    [switch]$WarningFlag,

    [parameter(HelpMessage="Specifies an error.")]
    [alias("e")]
    [switch]$ErrorFlag,

    [parameter(HelpMessage="Specifies a fatal error.")]
    [alias("f")]
    [switch]$FatalFlag,

    [parameter(HelpMessage="Specifies a info message.")]
    [alias("i")]
    [switch]$InfoFlag = !$SuccessFlag -and !$WarningFlag -and !$ErrorFlag -and !$FatalFlag,

    [parameter(HelpMessage="Specifies blank lines to print before.")]
    [alias("b")]
    [int]$LinesBefore=0,

    [parameter(HelpMessage="Specifies blank lines to print after.")]
    [alias("a")]
    [int]$LinesAfter=0,

    [parameter(HelpMessage="Specifies if program should exit.")]
    [alias("x")]
    [switch]$ExitAfter
  )
  PROCESS {
    if($LinesBefore -ne 0) {
      foreach($i in 0..$LinesBefore) { Write-Host "" }
    }
    if($InfoFlag) { Write-Host "$Message" }
    if($SuccessFlag) { Write-Host "$Message" -ForegroundColor "Green" }
    if($WarningFlag) { Write-Host "$Message" -ForegroundColor "Orange" }
    if($ErrorFlag) { Write-Host "$Message" -ForegroundColor "Red" }
    if($FatalFlag) { Write-Host "$Message" -ForegroundColor "Red" -BackgroundColor "Black" }
    if($LinesAfter -ne 0) {
      foreach($i in 0..$LinesAfter) { Write-Host "" }
    }
    if($ExitAfter) { SafeExit }
  }
}

# VALIDATES STRING MIGHT BE A PATH #
function ValidatePath($PathName, $TestPath) {
  If([string]::IsNullOrWhiteSpace($TestPath)) {
    Print -x -f "$PathName is not a path"
  }
}

# NORMALIZES RELATIVE OR ABSOLUTE PATH TO ABSOLUTE PATH #
function NormalizePath($PathName, $TestPath) {
  ValidatePath "$PathName" "$TestPath"
  $TestPath = [System.IO.Path]::Combine((pwd).Path, $TestPath)
  $NormalizedPath = [System.IO.Path]::GetFullPath($TestPath)
  return $NormalizedPath
}


# VALIDATES STRING MIGHT BE A PATH AND RETURNS ABSOLUTE PATH #
function ResolvePath($PathName, $TestPath) {
  ValidatePath "$PathName" "$TestPath"
  $ResolvedPath = NormalizePath $PathName $TestPath
  return $ResolvedPath
}

# VALIDATES STRING RESOLVES TO A PATH AND RETURNS ABSOLUTE PATH #
function RequirePath($PathName, $TestPath, $PathType) {
  ValidatePath $PathName $TestPath
  If(!(Test-Path $TestPath -PathType $PathType)) {
    Print -x -f "$PathName ($TestPath) does not exist as a $PathType"
  }
  $ResolvedPath = Resolve-Path $TestPath
  return $ResolvedPath
}

# Like mkdir -p -> creates a directory recursively if it doesn't exist #
function MakeDirP {
  [CmdletBinding()]
  param (
    [parameter(Mandatory=$TRUE,Position=0,HelpMessage="Path create.")]
    [string]$Path
  )
  PROCESS {
    New-Item -path $Path -itemtype Directory -force | Out-Null
  }
}

# GETS ALL FILES IN A PATH RECURSIVELY #
function GetFiles {
  [CmdletBinding()]
  param (
    [parameter(Mandatory=$TRUE,Position=0,HelpMessage="Path to get files for.")]
    [string]$Path
  )
  PROCESS {
    ls $Path -r | where { !$_.PSIsContainer }
  }
}

# GETS ALL FILES WITH CALCULATED HASH PROPERTY RELATIVE TO A ROOT DIRECTORY RECURSIVELY #
# RETURNS LIST OF @{RelativePath, Hash, FullName}
function GetFilesWithHash {
  [CmdletBinding()]
  param (
    [parameter(Mandatory=$TRUE,Position=0,HelpMessage="Path to get directories for.")]
    [string]$Path,

    [parameter(HelpMessage="The hash algorithm to use.")]
    [string]$Algorithm="MD5"
  )
  PROCESS {
    $OriginalPath = $PWD
    SetWorkDir path/to/diff $Path
    GetFiles $Path | select @{N="RelativePath";E={$_.FullName | Resolve-Path -Relative}},
                            @{N="Hash";E={(Get-FileHash $_.FullName -Algorithm $Algorithm | select Hash).Hash}},
                            FullName
    SetWorkDir path/to/original $OriginalPath
  }
}

# COMPARE TWO DIRECTORIES RECURSIVELY #
# RETURNS LIST OF @{RelativePath, Hash, FullName}
function DiffDirectories {
  [CmdletBinding()]
  param (
    [parameter(Mandatory=$TRUE,Position=0,HelpMessage="Directory to compare left.")]
    [alias("l")]
    [string]$LeftPath,

    [parameter(Mandatory=$TRUE,Position=1,HelpMessage="Directory to compare right.")]
    [alias("r")]
    [string]$RightPath
  )
  PROCESS {
    $LeftHash = GetFilesWithHash $LeftPath
    $RightHash = GetFilesWithHash $RightPath
    diff -ReferenceObject $LeftHash -DifferenceObject $RightHash -Property RelativePath,Hash
  }
}

### END FUNCTION DEFINITIONS ###

### PROGRAM LOGIC ###

if($Compare.length -ne 2) {
  Print -x "Compare requires passing exactly 2 path parameters separated by comma, you passed $($Compare.length)." -f
}
Print "Comparing $($Compare[0]) to $($Compare[1])..." -a 1
$LeftPath   = RequirePath path/to/left $Compare[0] container
$RightPath  = RequirePath path/to/right $Compare[1] container
$Diff       = DiffDirectories $LeftPath $RightPath
$LeftDiff   = $Diff | where {$_.SideIndicator -eq "<="} | select RelativePath,Hash
$RightDiff   = $Diff | where {$_.SideIndicator -eq "=>"} | select RelativePath,Hash
if($ExportSummary) {
  $ExportSummary = ResolvePath path/to/summary/dir $ExportSummary
  MakeDirP $ExportSummary
  $SummaryPath = Join-Path $ExportSummary summary.txt
  $LeftCsvPath = Join-Path $ExportSummary left.csv
  $RightCsvPath = Join-Path $ExportSummary right.csv

  $LeftMeasure = $LeftDiff | measure
  $RightMeasure = $RightDiff | measure

  "== DIFF SUMMARY ==" > $SummaryPath
  "" >> $SummaryPath
  "-- DIRECTORIES --" >> $SummaryPath
  "`tLEFT -> $LeftPath" >> $SummaryPath
  "`tRIGHT -> $RightPath" >> $SummaryPath
  "" >> $SummaryPath
  "-- DIFF COUNT --" >> $SummaryPath
  "`tLEFT -> $($LeftMeasure.Count)" >> $SummaryPath
  "`tRIGHT -> $($RightMeasure.Count)" >> $SummaryPath
  "" >> $SummaryPath
  $Diff | Format-Table >> $SummaryPath

  $LeftDiff | Export-Csv $LeftCsvPath -f
  $RightDiff | Export-Csv $RightCsvPath -f
}
$Diff
SafeExit

This is really nice Powershell script. Good work!

Very helpful, thanks for posting this!