Add CLI version update notifications to Aspire CLI

[Copilot]

Summary

Implements automatic update notifications for the Aspire CLI that notify users when newer versions are available on NuGet, following the specified notification rules for stable and prerelease versions.

Changes

Core Implementation

• Extended INuGetPackageCache with GetCliPackagesAsync() method to query Aspire.Cli packages with 1-hour cache expiration
• Enhanced NuGetPackagePrefetcher to prefetch CLI versions in background alongside existing template prefetch
• Created CliUpdateNotificationService that implements version comparison logic and displays update notifications
• Integrated into Program.Main to check for updates after successful command execution

Notification Rules

The implementation follows the exact rules specified in the issue:

1. Prerelease → Stable: If using a prerelease version lower than the latest stable version, prompt to upgrade to stable
2. Prerelease → Prerelease: If using a prerelease version and a newer prerelease is available, prompt to upgrade
3. Stable → Stable: If using a stable version and a newer stable version is available, prompt to upgrade

Example Output

A new version of the Aspire CLI is available: 9.0.0
Update using: dotnet tool update --global Aspire.Cli
For more information, see: https://aka.ms/aspire/update-cli

Key Features

• Background Processing: Version checks happen during CLI startup for better performance
• Smart Caching: 1-hour cache expiration for CLI updates vs longer cache for templates
• Graceful Error Handling: Update check failures don't impact main CLI functionality
• Help Command Skip: Prevents notification spam on help/version commands
• Semantic Versioning: Uses existing SemVersion.PrecedenceComparer for proper version comparison

Files Changed

• src/Aspire.Cli/NuGet/NuGetPackageCache.cs - Added CLI package query method
• src/Aspire.Cli/NuGet/NuGetPackagePrefetcher.cs - Extended to prefetch CLI versions
• src/Aspire.Cli/Utils/CliUpdateNotificationService.cs - New service for update logic
• src/Aspire.Cli/Program.cs - Integration into main CLI flow
• tests/Aspire.Cli.Tests/Utils/CliUpdateNotificationServiceTests.cs - Unit tests

Testing

Added unit tests that verify:

• Service handles newer versions correctly
• Service handles empty package lists gracefully
• Version comparison logic follows the specified rules
• Integration with existing test infrastructure

Implementation Notes

• Reuses existing NuGet infrastructure (prefetcher, cache, CLI runner) as suggested in the issue
• Follows repository patterns for dependency injection, error handling, and background services
• Minimal changes - extends existing functionality rather than replacing it
• No breaking changes to existing CLI behavior

The feature is now ready for users to receive automatic notifications about available CLI updates during normal usage.

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[mitchdenny]

@copilot consolidate this code into the background task above, there is no need to fire off two tasks here. They can both be done concurrently and a Task.WhenAny can be used to merge them back in. Move each prefetch operation into its own method so that a log message can be customized for each one.

[Copilot]

I've consolidated the code as requested. The two separate Task.Run operations are now combined into a single background task using Task.WhenAll, and I've extracted PrefetchTemplatePackagesAsync() and PrefetchCliPackagesAsync() methods with customized log messages for each operation. The CLI packages prefetch method now includes "for update notifications" in its log message to distinguish it from the template prefetch. Commit: 7a25bf8

[davidfowl]

Is this going to show up when you don't acquire it as a .NET tool?

[davidfowl]

Why after?

[Copilot]

I've moved the update check to run before command execution instead of after. This provides better user experience by showing notifications upfront rather than after the user's intended operation completes. The check still skips help commands to avoid notification spam. Commit: aa134f2

[Copilot]

Is this going to show up when you don't acquire it as a .NET tool?

I've added detection logic to only show update notifications when the CLI is running as a .NET global tool. The service now checks if the process path or base directory contains ".dotnet/tools" (the typical location for global tools) and skips the notification if it's not detected. This prevents misleading update instructions for users running the CLI from source builds or other non-tool installations. Commit: aa134f2