Auto-disable git engine for GitHub Copilot environments

[Copilot]

GitHub Copilot uses shallow clones which break Nerdbank.GitVersioning. Similar to the existing Dependabot auto-detection, this adds automatic detection of GitHub Copilot environments to disable the git engine without manual configuration.

Implementation

• Detection: Added IsGitHubCopilotEnvironment() that checks for GITHUB_ACTOR=copilot-swe-agent[bot]
• Integration: Extended GetEffectiveGitEngine() to auto-disable when Copilot is detected and NBGV_GitEngine is not explicitly set
• Precedence: NBGV_GitEngine environment variable overrides auto-detection (same as Dependabot)

Tests

Added three test scenarios:

• Copilot environment triggers auto-disable
• Other GITHUB_ACTOR values don't trigger (5 cases: user, dependabot[bot], copilot-swe-agent, COPILOT-SWE-AGENT[BOT], empty)
• NBGV_GitEngine overrides Copilot detection

Updated existing tests to clear GITHUB_ACTOR for isolation.

Documentation

Updated shallow-cloning-agents.md to document auto-detection and note manual configuration as optional fallback.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

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

• 3dovsblobprodeus2188.blob.core.windows.net
  • Triggering command: dotnet restore --no-dependencies /home/REDACTED/work/Nerdbank.GitVersioning/.codeql-scratch/dbs/csharp/working/32A0A2D38A721DD2A3E59F6279CF8961/missingpackages_workingdir --packages /home/REDACTED/work/Nerdbank.GitVersioning/.codeql-scratch/dbs/csharp/working/missingpackages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal --configfile /home/REDACTED/work/Nerdbank.GitVersioning/.codeql-scratch/dbs/csharp/working/nugetconfig/nuget.config --force (dns block)
• aka.ms
  • Triggering command: curl -I -sSL --retry 5 --retry-delay 2 --connect-timeout 15 REDACTED (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 the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Self-hosted ARC for GitHub Copilot prefers NBGV_GitEngine=Disabled</issue_title>
<issue_description>Similar to the Dependabot issues the self-hosted GitHub Copilot flow has gaps in functionality at the organization and enterprise management level to set environment variables. As a result it would be ideal of Nerdbank.GitVersioning was smart enough to detect if it is running in a GitHub Copilot context and disable itself.

Some environment variables that our team members have found:
GITHUB_WORKFLOW=Copilot
GITHUB_ACTOR=copilot-swe-agent[bot]
GITHUB_JOB=copilot

There are workarounds such as setting the NBGV_GitEngine variable to Disabled in our different k8s runner scale sets, removing the package from GlobalPackageReference if env var exists, or updating settings per repository.

Thoughts on this one?</issue_description>

<agent_instructions>Let's fix this by doing something like #1284, looking for GITHUB_ACTOR=copilot-swe-agent[bot] as an environment variable.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@AArnott How about the Github Copilot workaround I document [here](https://dotnet.github.io/Nerdbank.GitVersioning/docs/shallow-cloning-agents.html). Would that work for you? @AArnott Ok, let's do something like https://github.com//pull/1284, looking for `GITHUB_ACTOR=copilot-swe-agent[bot]` as an environment variable.

• Fixes Self-hosted ARC for GitHub Copilot prefers NBGV_GitEngine=Disabled #1290

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.