Get-FolderHash -- a PowerShell function for computing the SHA1 hash of an entire folder's contents

Get-FolderHash.ps1

# Source: https://social.technet.microsoft.com/Forums/en-US/2e7db624-2260-4a65-a57b-f6f2e22312f0/sha1-hash-of-an-entire-folder-structure
Function Get-FolderHash ($folder) {
  Get-ChildItem $folder -Recurse |
    Where-Object {!$_.psiscontainer} |
    ForEach-Object {[Byte[]]$contents += [System.IO.File]::ReadAllBytes($_.fullname)}
  $hasher = [System.Security.Cryptography.SHA1]::Create()
  [string]::Join("",$($hasher.ComputeHash($contents) | ForEach-Object {"{0:x2}" -f $_}))
}