Provide an install.ps1 PowerShell script to install opam on Windows

shell/install.ps1

@@ -0,0 +1,87 @@
+param (
+  [bool]$Dev = $false,
+  [string]$Version = "2.2.0~beta2"
+)
+
+$DevVersion = "2.2.0~beta2"
+$DefaultBinDir = "$Env:ProgramFiles\opam\bin"
+
+Function GetArch {
+  switch ($Env:PROCESSOR_ARCHITECTURE) {
+    "AMD64" { "x86_64" }
+    "Arm64" { "arm64" }
+    "x86" { "i686" }
+    Default { throw "Unknown architecture" }
+  }
+}
+
+Function BinSHA512 {
+  param (
+    [string]$OpamBinName
+  )
+
+  switch ($OpamBinName) {
+    "opam-2.2.0-beta2-x86_64-windows.exe" { "74f034ccc30ef0b2041283ff125be2eab565d4019e79f946b515046c4c290a698266003445f38b91321a9ef931093651f861360906ff06c076c24d18657e2aaf" }
+    Default { throw "no sha" }
+  }
+}
+
+Function CheckSHA512 {
+  param (
+    [string]$OpamBinTmpLoc,
+    [string]$OpamBinName
+  )
+
+  $Hash = (CertUtil -hashfile "$OpamBinTmpLoc" SHA512)[1]
+  $HashTarget = BinSHA512 -OpamBinName "$OpamBinName"
+
+  if ("$Hash" -ne "$HashTarget") {
+    throw "Checksum does not match"
+  }
+}
+
+Function DownloadAndCheck {
+  param (
+    [string]$OpamBinUrl,
+    [string]$OpamBinTmpLoc,
+    [string]$OpamBinName
+  )
+
+  Start-BitsTransfer -Source "$OpamBinUrl" -Destination "$OpamBinTmpLoc"
+  CheckSHA512 -OpamBinTmpLoc "$OpamBinTmpLoc" -OpamBinName "$OpamBinName"
+}
+
+if ($Dev) {
+  $Version = $DevVersion
+}
+
+$Tag = $Version -creplace "~", "-"
+$Arch = GetArch
+$OS = "windows"
+$OpamBinUrlBase = "https://github.com/ocaml/opam/releases/download/"
+$OpamBinName = "opam-${Tag}-${Arch}-${OS}.exe"
+$OpamBinUrl = "${OpamBinUrlBase}${Tag}/${OpamBinName}"
+
+$OpamBinTmpLoc = "$Env:TMP\$OpamBinName"
+DownloadAndCheck -OpamBinUrl "$OpamBinUrl" -OpamBinTmpLoc "$OpamBinTmpLoc" -OpamBinName "$OpamBinName"
+
+$OpamBinDir = Read-Host "## Where should it be installed? [$DefaultBinDir]"
+if ($OpamBinDir -eq "") {
+  $OpamBinDir = $DefaultBinDir
+}
+
+if (($OpamBinDir -contains "'") -or ($OpamBinTmpLoc -contains "'") -or ($OpamBinDir -contains '"')) {
+  throw "String contains unsupported characters"
+}
+
+Start-Process -FilePath powershell -Verb RunAs -ArgumentList '-Command', @"
+if (-not (Test-Path -Path '$OpamBinDir' -PathType Container)) {
+  New-Item '$OpamBinDir' -Type Directory -Force
+}
+Move-Item -Path '$OpamBinTmpLoc' -Destination '${OpamBinDir}\opam.exe'
+
+`$PATH = [Environment]::GetEnvironmentVariable('PATH', 'MACHINE')
+if (-not (`$PATH -contains '$OpamBinDir')) {
+  [Environment]::SetEnvironmentVariable('PATH', '${OpamBinDir};'+`$PATH, 'MACHINE')
+}
+"@