Refactor dotnet download code in init-tools.cmd (dotnet#10527)

* Refactor dotnet download code in init-tools.cmd
This addresses the improvements proposed in issue #10526.
Includes the init-tools.cmd script refactor and a new script called
dotnet-download.ps1 which includes the extracted code and logic

* Code review feedback changes

* Fix spacing

dotnet-download.ps1

@@ -0,0 +1,37 @@
+param(
+    [parameter(Mandatory=$true)]$DotnetRemotePath,
+    [parameter(Mandatory=$true)]$DotnetLocalPath,
+    [parameter(Mandatory=$true)]$DotnetPath
+)
+
+$retryCount = 0
+$success = $false
+
+do {
+    try {
+        Write-Output "Downloading from $DotnetRemotePath"
+        (New-Object Net.WebClient).DownloadFile($DotnetRemotePath, $DotnetLocalPath)
+        $success = $true
+    } catch { 
+        if ($retryCount -ge 6) {
+            Write-Output "Maximum of 5 retries exceeded. Aborting"
+            throw
+        } 
+        else { 
+            $retryCount++
+            $retryTime = 5 * $retryCount
+            Write-Output "Download failed. Retrying in $retryTime seconds"
+            Start-Sleep -Seconds (5 * $retryCount)
+        }
+    }
+} while ($success -eq $false)
+
+Write-Output "Download finished"
+Add-Type -Assembly 'System.IO.Compression.FileSystem' -ErrorVariable AddTypeErrors
+
+if ($AddTypeErrors.Count -eq 0) { 
+    [System.IO.Compression.ZipFile]::ExtractToDirectory($DotnetLocalPath, $DotnetPath) 
+}
+else { 
+    (New-Object -com shell.application).namespace($DotnetPath).CopyHere((new-object -com shell.application).namespace($DotnetLocalPath).Items(), 16)
+}

init-tools.cmd

@@ -4,6 +4,8 @@ setlocal
 set INIT_TOOLS_LOG=%~dp0init-tools.log
 set PACKAGES_DIR=%~dp0packages\
 set TOOLRUNTIME_DIR=%~dp0Tools
+:: This is an isolated script that handles the download of dotnet binaries and shall be removed after bootstrap.ps1/sh refactor (dotnet/corefx#15427)
+set DOTNET_DOWNLOAD_PATH=%~dp0dotnet-download.ps1
 set DOTNET_PATH=%TOOLRUNTIME_DIR%\dotnetcli\
 set DOTNET_CMD=%DOTNET_PATH%dotnet.exe
 if [%BUILDTOOLS_SOURCE%]==[] set BUILDTOOLS_SOURCE=https://dotnet.myget.org/F/dotnet-buildtools/api/v3/index.json
@@ -48,7 +50,7 @@ if [%PROCESSOR_ARCHITECTURE%]==[x86] (set DOTNET_ZIP_NAME=dotnet-dev-win-x86.%DO
 set DOTNET_REMOTE_PATH=https://dotnetcli.blob.core.windows.net/dotnet/preview/Binaries/%DOTNET_VERSION%/%DOTNET_ZIP_NAME%
 set DOTNET_LOCAL_PATH=%DOTNET_PATH%%DOTNET_ZIP_NAME%
 echo Installing '%DOTNET_REMOTE_PATH%' to '%DOTNET_LOCAL_PATH%' >> "%INIT_TOOLS_LOG%"
-powershell -NoProfile -ExecutionPolicy unrestricted -Command "$retryCount = 0; $success = $false; do { try { (New-Object Net.WebClient).DownloadFile('%DOTNET_REMOTE_PATH%', '%DOTNET_LOCAL_PATH%'); $success = $true; } catch { if ($retryCount -ge 6) { throw; } else { $retryCount++; Start-Sleep -Seconds (5 * $retryCount); } } } while ($success -eq $false); Add-Type -Assembly 'System.IO.Compression.FileSystem' -ErrorVariable AddTypeErrors; if ($AddTypeErrors.Count -eq 0) { [System.IO.Compression.ZipFile]::ExtractToDirectory('%DOTNET_LOCAL_PATH%', '%DOTNET_PATH%') } else { (New-Object -com shell.application).namespace('%DOTNET_PATH%').CopyHere((new-object -com shell.application).namespace('%DOTNET_LOCAL_PATH%').Items(),16) }" >> "%INIT_TOOLS_LOG%"
+powershell -NoProfile -ExecutionPolicy unrestricted -File %DOTNET_DOWNLOAD_PATH% -DotnetRemotePath %DOTNET_REMOTE_PATH% -DotnetLocalPath %DOTNET_LOCAL_PATH% -DotnetPath %DOTNET_PATH% >> "%INIT_TOOLS_LOG%"
 if NOT exist "%DOTNET_LOCAL_PATH%" (
   echo ERROR: Could not install dotnet cli correctly. See '%INIT_TOOLS_LOG%' for more details.
   set TOOLS_INIT_RETURN_CODE=1