Install-Msys2.ps1

function Install-Msys2 () {
  param (
    [Parameter()] [String] $Dir = 'c:\tools\msys2'
  )
  if (Test-Path $Dir -PathType Any) {
    $reply = Read-Host -Prompt "MSys2 destination $Dir exists. Delete and continue? [y/n]"
    if ($reply -eq 'y') {
      Remove-Item -Recurse -Force $Dir
    } else {
      return
    }
  }
  $archive = Join-Path $env:TEMP 'msys2.tar.xz'
  Invoke-WebRequest -Uri 'http://repo.msys2.org/distrib/msys2-x86_64-latest.tar.xz' -OutFile $archive -UseBasicParsing
  & 7z 'e' '-y' "-o$Dir" $archive
  & 7z 'x' '-y' "-o$Dir" (Join-Path $Dir 'msys2.tar')

  $bash = Join-Path $Dir 'msys64\usr\bin\bash.exe'
  $msysShell = Join-Path $Dir 'msys64\msys2_shell.cmd'
  # Run initial command so bash configures itself.
  & $msysShell '-msys2' '-no-start' '-shell' 'bash' '-l' '-c' '"echo"'
  # Update; couple of times since this might need restarts.
  & $msysShell '-msys2' '-no-start' '-shell' 'bash' '-l' '-c' '"pacman -Syuu --noconfirm"'
  & $msysShell '-msys2' '-no-start' '-shell' 'bash' '-l' '-c' '"pacman -Syuu --noconfirm"'
  & $msysShell '-msys2' '-no-start' '-shell' 'bash' '-l' '-c' '"pacman -Syuu --noconfirm"'
  # Install gcc etc.
  & $msysShell '-msys2' '-no-start' '-shell' 'bash' '-l' '-c' '"pacman -S --noconfirm make mingw-w64-x86_64-gcc pkg-config"'
}