Auto-disable git engine for GitHub Copilot environments

docfx/docs/shallow-cloning-agents.md

@@ -15,7 +15,15 @@ A few caveats with this:
 
 ## GitHub Copilot Coding Agent
 
-To configure the Copilot Coding Agent to set this environment variable, follow these steps to set environment variables for the `copilot` environment:
+**As of Nerdbank.GitVersioning v3.9, the git engine is automatically disabled when running under GitHub Copilot**, eliminating the need for manual configuration in most cases.
+
+Specifically, when the `GITHUB_ACTOR` environment variable is set to `copilot-swe-agent[bot]` and the `NBGV_GitEngine` environment variable is **not** set, Nerdbank.GitVersioning automatically behaves as if `NBGV_GitEngine=Disabled`. This ensures that GitHub Copilot runs succeed without any additional setup.
+
+If you need to override this behavior for any reason, you can explicitly set the `NBGV_GitEngine` environment variable to your desired value, which will take precedence over the automatic GitHub Copilot detection.
+
+### Manual configuration (optional)
+
+If automatic detection doesn't work for your scenario, you can manually configure the Copilot Coding Agent to set the environment variable by following these steps to set environment variables for the `copilot` environment:
 
 1. Navigate to your GitHub repo's Settings tab.
 1. Select Environments from the list on the left.

src/NerdBank.GitVersioning/GitContext.cs

@@ -134,7 +134,7 @@ public string RepoRelativeProjectDirectory
     protected string? DotGitPath { get; }
 
     /// <summary>
-    /// Gets the effective git engine to use, taking into account automatic disabling for Dependabot.
+    /// Gets the effective git engine to use, taking into account automatic disabling for Dependabot and GitHub Copilot.
     /// This overload checks the NBGV_GitEngine environment variable and parses it automatically.
     /// </summary>
     /// <param name="defaultEngine">The engine to use if no environment variables dictate otherwise.</param>
@@ -144,11 +144,12 @@ public string RepoRelativeProjectDirectory
     /// Valid values are "LibGit2", "Managed", and "Disabled" (case-sensitive).
     /// Unrecognized values are treated as if the variable was not set, maintaining backward compatibility.
     /// Otherwise, if the DEPENDABOT environment variable is set to "true" (case-insensitive), returns <see cref="Engine.Disabled"/>.
+    /// Otherwise, if the GITHUB_ACTOR environment variable is set to "copilot-swe-agent[bot]", returns <see cref="Engine.Disabled"/>.
     /// Otherwise, returns <paramref name="defaultEngine"/>.
     /// </remarks>
     public static Engine GetEffectiveGitEngine(Engine defaultEngine = Engine.ReadOnly)
     {
-        // If NBGV_GitEngine is set, respect that setting regardless of Dependabot
+        // If NBGV_GitEngine is set, respect that setting regardless of Dependabot or GitHub Copilot
         string? nbgvGitEngine = Environment.GetEnvironmentVariable("NBGV_GitEngine");
         if (!string.IsNullOrEmpty(nbgvGitEngine))
         {
@@ -177,6 +178,12 @@ public static Engine GetEffectiveGitEngine(Engine defaultEngine = Engine.ReadOnl
             return Engine.Disabled;
         }
 
+        // If we're in a GitHub Copilot environment and NBGV_GitEngine is not set, automatically disable the git engine
+        if (IsGitHubCopilotEnvironment())
+        {
+            return Engine.Disabled;
+        }
+
         // Otherwise, use the default engine
         return defaultEngine;
     }
@@ -398,4 +405,14 @@ private static bool IsDependabotEnvironment()
         string? dependabotEnvVar = Environment.GetEnvironmentVariable("DEPENDABOT");
         return string.Equals(dependabotEnvVar, "true", StringComparison.OrdinalIgnoreCase);
     }
+
+    /// <summary>
+    /// Determines whether the current environment is running under GitHub Copilot.
+    /// </summary>
+    /// <returns><see langword="true"/> if GITHUB_ACTOR environment variable is set to "copilot-swe-agent[bot]"; otherwise, <see langword="false"/>.</returns>
+    private static bool IsGitHubCopilotEnvironment()
+    {
+        string? githubActorEnvVar = Environment.GetEnvironmentVariable("GITHUB_ACTOR");
+        return string.Equals(githubActorEnvVar, "copilot-swe-agent[bot]", StringComparison.Ordinal);
+    }
 }

test/Nerdbank.GitVersioning.Tests/GitContextTests.cs

@@ -193,13 +193,15 @@ public void HeadCanonicalName_PackedHead()
     [Fact]
     public void GetEffectiveGitEngine_DefaultBehavior()
     {
-        // Arrange: Clear both environment variables
+        // Arrange: Clear all environment variables
         var originalDependabot = Environment.GetEnvironmentVariable("DEPENDABOT");
         var originalNbgvGitEngine = Environment.GetEnvironmentVariable("NBGV_GitEngine");
+        var originalGitHubActor = Environment.GetEnvironmentVariable("GITHUB_ACTOR");
         try
         {
             Environment.SetEnvironmentVariable("DEPENDABOT", null);
             Environment.SetEnvironmentVariable("NBGV_GitEngine", null);
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", null);
 
             // Act & Assert: With no environment variables, should return default ReadOnly
             Assert.Equal(GitContext.Engine.ReadOnly, GitContext.GetEffectiveGitEngine());
@@ -209,6 +211,7 @@ public void GetEffectiveGitEngine_DefaultBehavior()
         {
             Environment.SetEnvironmentVariable("DEPENDABOT", originalDependabot);
             Environment.SetEnvironmentVariable("NBGV_GitEngine", originalNbgvGitEngine);
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", originalGitHubActor);
         }
     }
 
@@ -218,13 +221,15 @@ public void GetEffectiveGitEngine_DefaultBehavior()
     [InlineData("True")]
     public void GetEffectiveGitEngine_DependabotEnvironment_DisablesEngine(string dependabotValue)
     {
-        // Arrange: Set DEPENDABOT=true and clear NBGV_GitEngine
+        // Arrange: Set DEPENDABOT=true and clear NBGV_GitEngine and GITHUB_ACTOR
         var originalDependabot = Environment.GetEnvironmentVariable("DEPENDABOT");
         var originalNbgvGitEngine = Environment.GetEnvironmentVariable("NBGV_GitEngine");
+        var originalGitHubActor = Environment.GetEnvironmentVariable("GITHUB_ACTOR");
         try
         {
             Environment.SetEnvironmentVariable("DEPENDABOT", dependabotValue);
             Environment.SetEnvironmentVariable("NBGV_GitEngine", null);
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", null);
 
             // Act & Assert: Should return Disabled regardless of requested engine
             Assert.Equal(GitContext.Engine.Disabled, GitContext.GetEffectiveGitEngine());
@@ -235,6 +240,7 @@ public void GetEffectiveGitEngine_DependabotEnvironment_DisablesEngine(string de
         {
             Environment.SetEnvironmentVariable("DEPENDABOT", originalDependabot);
             Environment.SetEnvironmentVariable("NBGV_GitEngine", originalNbgvGitEngine);
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", originalGitHubActor);
         }
     }
 
@@ -245,13 +251,15 @@ public void GetEffectiveGitEngine_DependabotEnvironment_DisablesEngine(string de
     [InlineData("")]
     public void GetEffectiveGitEngine_DependabotNotTrue_UsesDefault(string dependabotValue)
     {
-        // Arrange: Set DEPENDABOT to non-true value and clear NBGV_GitEngine
+        // Arrange: Set DEPENDABOT to non-true value and clear NBGV_GitEngine and GITHUB_ACTOR
         var originalDependabot = Environment.GetEnvironmentVariable("DEPENDABOT");
         var originalNbgvGitEngine = Environment.GetEnvironmentVariable("NBGV_GitEngine");
+        var originalGitHubActor = Environment.GetEnvironmentVariable("GITHUB_ACTOR");
         try
         {
             Environment.SetEnvironmentVariable("DEPENDABOT", dependabotValue);
             Environment.SetEnvironmentVariable("NBGV_GitEngine", null);
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", null);
 
             // Act & Assert: Should use default behavior
             Assert.Equal(GitContext.Engine.ReadOnly, GitContext.GetEffectiveGitEngine());
@@ -261,6 +269,7 @@ public void GetEffectiveGitEngine_DependabotNotTrue_UsesDefault(string dependabo
         {
             Environment.SetEnvironmentVariable("DEPENDABOT", originalDependabot);
             Environment.SetEnvironmentVariable("NBGV_GitEngine", originalNbgvGitEngine);
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", originalGitHubActor);
         }
     }
 
@@ -270,13 +279,15 @@ public void GetEffectiveGitEngine_DependabotNotTrue_UsesDefault(string dependabo
     [InlineData("Disabled", GitContext.Engine.Disabled)]
     public void GetEffectiveGitEngine_NbgvGitEngineOverridesDependabot(string nbgvValue, GitContext.Engine expectedEngine)
     {
-        // Arrange: Set both DEPENDABOT and NBGV_GitEngine
+        // Arrange: Set both DEPENDABOT and NBGV_GitEngine, clear GITHUB_ACTOR
         var originalDependabot = Environment.GetEnvironmentVariable("DEPENDABOT");
         var originalNbgvGitEngine = Environment.GetEnvironmentVariable("NBGV_GitEngine");
+        var originalGitHubActor = Environment.GetEnvironmentVariable("GITHUB_ACTOR");
         try
         {
             Environment.SetEnvironmentVariable("DEPENDABOT", "true");
             Environment.SetEnvironmentVariable("NBGV_GitEngine", nbgvValue);
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", null);
 
             // Act & Assert: NBGV_GitEngine should take precedence and be parsed correctly
             Assert.Equal(expectedEngine, GitContext.GetEffectiveGitEngine());
@@ -285,6 +296,87 @@ public void GetEffectiveGitEngine_NbgvGitEngineOverridesDependabot(string nbgvVa
         {
             Environment.SetEnvironmentVariable("DEPENDABOT", originalDependabot);
             Environment.SetEnvironmentVariable("NBGV_GitEngine", originalNbgvGitEngine);
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", originalGitHubActor);
+        }
+    }
+
+    [Fact]
+    public void GetEffectiveGitEngine_GitHubCopilotEnvironment_DisablesEngine()
+    {
+        // Arrange: Set GITHUB_ACTOR to copilot-swe-agent[bot] and clear NBGV_GitEngine and DEPENDABOT
+        var originalGitHubActor = Environment.GetEnvironmentVariable("GITHUB_ACTOR");
+        var originalNbgvGitEngine = Environment.GetEnvironmentVariable("NBGV_GitEngine");
+        var originalDependabot = Environment.GetEnvironmentVariable("DEPENDABOT");
+        try
+        {
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", "copilot-swe-agent[bot]");
+            Environment.SetEnvironmentVariable("NBGV_GitEngine", null);
+            Environment.SetEnvironmentVariable("DEPENDABOT", null);
+
+            // Act & Assert: Should return Disabled regardless of requested engine
+            Assert.Equal(GitContext.Engine.Disabled, GitContext.GetEffectiveGitEngine());
+            Assert.Equal(GitContext.Engine.Disabled, GitContext.GetEffectiveGitEngine(GitContext.Engine.ReadOnly));
+            Assert.Equal(GitContext.Engine.Disabled, GitContext.GetEffectiveGitEngine(GitContext.Engine.ReadWrite));
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", originalGitHubActor);
+            Environment.SetEnvironmentVariable("NBGV_GitEngine", originalNbgvGitEngine);
+            Environment.SetEnvironmentVariable("DEPENDABOT", originalDependabot);
+        }
+    }
+
+    [Theory]
+    [InlineData("user")]
+    [InlineData("dependabot[bot]")]
+    [InlineData("copilot-swe-agent")]
+    [InlineData("COPILOT-SWE-AGENT[BOT]")]
+    [InlineData("")]
+    public void GetEffectiveGitEngine_GitHubActorNotCopilot_UsesDefault(string gitHubActorValue)
+    {
+        // Arrange: Set GITHUB_ACTOR to non-copilot value and clear NBGV_GitEngine and DEPENDABOT
+        var originalGitHubActor = Environment.GetEnvironmentVariable("GITHUB_ACTOR");
+        var originalNbgvGitEngine = Environment.GetEnvironmentVariable("NBGV_GitEngine");
+        var originalDependabot = Environment.GetEnvironmentVariable("DEPENDABOT");
+        try
+        {
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", gitHubActorValue);
+            Environment.SetEnvironmentVariable("NBGV_GitEngine", null);
+            Environment.SetEnvironmentVariable("DEPENDABOT", null);
+
+            // Act & Assert: Should use default behavior
+            Assert.Equal(GitContext.Engine.ReadOnly, GitContext.GetEffectiveGitEngine());
+            Assert.Equal(GitContext.Engine.ReadWrite, GitContext.GetEffectiveGitEngine(GitContext.Engine.ReadWrite));
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", originalGitHubActor);
+            Environment.SetEnvironmentVariable("NBGV_GitEngine", originalNbgvGitEngine);
+            Environment.SetEnvironmentVariable("DEPENDABOT", originalDependabot);
+        }
+    }
+
+    [Theory]
+    [InlineData("LibGit2", GitContext.Engine.ReadWrite)]
+    [InlineData("Managed", GitContext.Engine.ReadOnly)]
+    [InlineData("Disabled", GitContext.Engine.Disabled)]
+    public void GetEffectiveGitEngine_NbgvGitEngineOverridesGitHubCopilot(string nbgvValue, GitContext.Engine expectedEngine)
+    {
+        // Arrange: Set both GITHUB_ACTOR=copilot-swe-agent[bot] and NBGV_GitEngine
+        var originalGitHubActor = Environment.GetEnvironmentVariable("GITHUB_ACTOR");
+        var originalNbgvGitEngine = Environment.GetEnvironmentVariable("NBGV_GitEngine");
+        try
+        {
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", "copilot-swe-agent[bot]");
+            Environment.SetEnvironmentVariable("NBGV_GitEngine", nbgvValue);
+
+            // Act & Assert: NBGV_GitEngine should take precedence and be parsed correctly
+            Assert.Equal(expectedEngine, GitContext.GetEffectiveGitEngine());
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("GITHUB_ACTOR", originalGitHubActor);
+            Environment.SetEnvironmentVariable("NBGV_GitEngine", originalNbgvGitEngine);
         }
     }
 }