Fix git tag pruning when fetching with specific refspecs

[Copilot]

This PR addresses a bug where --prune-tags doesn't work properly when git fetch is executed with specific refspecs (like in PR builds), causing conflicts when old and new tags have conflicting filesystem paths.

Problem

When PR builds fetch with refspecs like +refs/heads/*:refs/remotes/origin/* +refs/pull/<number>/merge:refs/remotes/pull/<number>/merge, git doesn't prune conflicting tag refs even with the --prune-tags flag, leading to errors like:

error: cannot lock ref 'refs/tags/one': 'refs/tags/one/two' exists; cannot create 'refs/tags/one'
! [new tag]               one              -> one  (unable to update local ref)

This happens because git's --prune-tags flag only works on refs that match the provided refspecs. Since PR build refspecs target branches and pull request refs (not tags), tag pruning doesn't happen even though new tags are still fetched.

Solution

Add git remote prune origin before fetching when we have specific refspecs and fetchTags is enabled, to clean up conflicting tag refs that would prevent new tags from being created.

Changes Made

1. Added GitRemotePrune method to both GitCommandManager (interface + implementation) and GitCliManager
2. Modified GitFetch methods in both classes to call GitRemotePrune before fetch when:
   • Specific refspecs are provided (refSpec is not null and has items)
   • Tag fetching is enabled (fetchTags is true)
   • Tag pruning is enabled (same conditions as existing --prune-tags)
3. Added test to verify GitRemotePrune is called for PR builds

Behavior

• Normal branch builds: No change - uses existing fetch behavior
• PR builds with tags: Now runs git remote prune origin before git fetch to clean up conflicting tag refs
• Error handling: If git remote prune fails, it logs the exit code but continues with fetch (non-breaking)

This is a minimal, surgical fix that addresses the specific git behavior while maintaining full backward compatibility.

Fixes #5170.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• 03nvsblobprodwcus014.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 055vsblobprodwcus02.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 1g1vsblobprodwcus01.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 3eavsblobprodwcus03.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 3zgvsblobprodwcus024.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 40qvsblobprodwcus022.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 4fdvsblobprodwcus012.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 5tbvsblobprodwcus06.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 61cvsblobprodwcus010.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 73dvsblobprodwcus07.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 8usvsblobprodwcus011.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• 9owvsblobprodwcus020.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• arpvsblobprodwcus017.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• crcvsblobprodwcus021.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• fslvsblobprodwcus015.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• grnvsblobprodwcus04.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• uubvsblobprodwcus018.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)
• vwmvsblobprodwcus016.vsblob.vsassets.io
  • Triggering command: dotnet build (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

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