get-dotnetup: pin daily shortlink to concrete build to avoid checksum race

scripts/get-dotnetup.ps1

@@ -140,6 +140,37 @@ function Get-RuntimeId {
 
 # --- Main ---
 
+# Map a 'channel' such as 'daily' to specific version url for the binary and its .sha512 to prevent release race condition mismatches
+function Resolve-FinalUrl([string]$Url) {
+    # Require an actual curl executable; on Windows PowerShell 5.1 'curl' is an alias for Invoke-WebRequest, so -CommandType Application excludes it.
+    $curl = Get-Command curl.exe -CommandType Application -ErrorAction SilentlyContinue
+    if (-not $curl) { $curl = Get-Command curl -CommandType Application -ErrorAction SilentlyContinue }
+    if ($curl) {
+        $sink = [System.IO.Path]::GetTempFileName()
+        try {
+            # --head resolves redirects without downloading the body.
+            $final = & $curl.Source --silent --show-error --location --head `
+                --output $sink --write-out '%{url_effective}' $Url 2>$null
+            if ($LASTEXITCODE -eq 0 -and $final) { return "$final".Trim() }
+        }
+        catch { }
+        finally { Remove-Item $sink -Force -ErrorAction SilentlyContinue }
+    }
+
+    # Fallback for hosts without a curl executable (e.g. Windows PowerShell 5.1):
+    try {
+        $req = [System.Net.WebRequest]::Create($Url)
+        $req.Method = "HEAD"
+        $req.AllowAutoRedirect = $true
+        $resp = $req.GetResponse()
+        try { return $resp.ResponseUri.AbsoluteUri }
+        finally { $resp.Dispose() }
+    }
+    catch {
+        return $null
+    }
+}
+
 $rid = Get-RuntimeId
 Write-Host "Detected runtime: $rid" -ForegroundColor Cyan
 
@@ -148,6 +179,17 @@ $fileName = if ($rid -like "win-*") { "dotnetup-$rid.exe" } else { "dotnetup-$ri
 $downloadUrl = "$BaseUrl/$fileName"
 $checksumUrl = "$downloadUrl.sha512"
 
+$resolvedUrl = Resolve-FinalUrl $downloadUrl
+if ($resolvedUrl -and $resolvedUrl -like "*/public/*") {
+    Write-Host "Resolved '$Quality' to concrete build: $resolvedUrl" -ForegroundColor DarkGray
+    $downloadUrl = $resolvedUrl
+    # Checksums live under the sibling 'public-checksums' path with a .sha512 suffix.
+    $checksumUrl = ($resolvedUrl -replace '/public/', '/public-checksums/') + ".sha512"
+}
+else {
+    Write-Host "Could not resolve '$Quality' shortlink to a concrete build; using shortlink URLs directly." -ForegroundColor DarkGray
+}
+
 $tempDir = Join-Path ([System.IO.Path]::GetTempPath()) "dotnetup-install-$([System.IO.Path]::GetRandomFileName())"
 New-Item -ItemType Directory -Path $tempDir -Force | Out-Null
 

scripts/get-dotnetup.sh

@@ -169,6 +169,32 @@ FILE_NAME="dotnetup-${RID}"
 DOWNLOAD_URL="${BASE_URL}/${FILE_NAME}"
 CHECKSUM_URL="${DOWNLOAD_URL}.sha512"
 
+# Map a 'channel' such as 'daily' to specific version url for the binary and its .sha512 to prevent release race condition mismatches
+resolve_final_url() {
+    local url="$1"
+    if [ "$DOWNLOADER" = "curl" ]; then
+        # --head resolves redirects without downloading the body.
+        curl --silent --show-error --location --head --output /dev/null \
+            --write-out '%{url_effective}' "$url" 2>/dev/null
+    elif [ "$DOWNLOADER" = "wget" ]; then
+        # wget lacks --write-out; --spider -S prints the redirect headers, whose final 'Location:' is the concrete build URL. tolower() keeps awk portable.
+        wget --spider -S "$url" 2>&1 \
+            | awk 'tolower($1) == "location:" { u = $2 } END { if (u != "") print u }'
+    fi
+    # An empty result falls back to the shortlink URLs below (previous behavior).
+}
+
+RESOLVED_URL="$(resolve_final_url "$DOWNLOAD_URL" || true)"
+if [ -n "$RESOLVED_URL" ] && [[ "$RESOLVED_URL" == *"/public/"* ]]; then
+    info "Resolved '${QUALITY}' to concrete build: $RESOLVED_URL"
+    DOWNLOAD_URL="$RESOLVED_URL"
+    # Checksums live under the sibling 'public-checksums' path. Use sed, not bash
+    # ${var/p/r}, since bash 3.2 (macOS) keeps the escaped backslashes literally.
+    CHECKSUM_URL="$(printf '%s' "$RESOLVED_URL" | sed 's#/public/#/public-checksums/#').sha512"
+else
+    gray "Could not resolve '${QUALITY}' shortlink to a concrete build; using shortlink URLs directly."
+fi
+
 INSTALLED_BINARY="${INSTALL_DIR}/dotnetup"
 
 TEMP_DIR=$(mktemp -d)