Improve Windows update parity

install.ps1

@@ -24,6 +24,24 @@ function Require-Command($Name) {
     }
 }
 
+function Ensure-Cargo {
+    if (Get-Command cargo -ErrorAction SilentlyContinue) {
+        return
+    }
+    if (-not (Get-Command winget -ErrorAction SilentlyContinue)) {
+        throw "cargo not found and winget is unavailable; install Rust from https://rustup.rs or set DOSH_USE_PREBUILT=1"
+    }
+    Write-Host "cargo not found; installing Rust toolchain with winget/rustup"
+    winget install --id Rustlang.Rustup -e --accept-package-agreements --accept-source-agreements
+    $cargoBin = Join-Path $HOME ".cargo\bin"
+    if (Test-Path $cargoBin) {
+        $env:Path = "$cargoBin;$env:Path"
+    }
+    if (-not (Get-Command cargo -ErrorAction SilentlyContinue)) {
+        throw "cargo was installed but is not available in this terminal yet; open a new terminal and rerun dosh update"
+    }
+}
+
 function Normalize-Arch {
     $arch = if ($env:PROCESSOR_ARCHITEW6432) { $env:PROCESSOR_ARCHITEW6432 } else { $env:PROCESSOR_ARCHITECTURE }
     switch ($arch) {
@@ -367,7 +385,7 @@ function Install-Prebuilt {
 }
 
 function Install-FromSource {
-    Require-Command cargo
+    Ensure-Cargo
     if (Test-Path "Cargo.toml") {
         $src = (Get-Location).Path
     } else {