Fix test failures when HOME is not a valid directory (issue #2227)

Co-authored-by: marekzmyslowski <1062877+marekzmyslowski@users.noreply.github.com>

Author: Copilot

src/shared/Core.Tests/GitConfigurationTests.cs

@@ -324,63 +324,58 @@ public void GitConfiguration_Set_All_ThrowsException()
         public void GitConfiguration_Unset_Global_UnsetsGlobalConfig()
         {
             string repoPath = CreateRepository(out string workDirPath);
-            try
-            {
-                ExecGit(repoPath, workDirPath, "config --global core.foobar alice").AssertSuccess();
-                ExecGit(repoPath, workDirPath, "config --local core.foobar bob").AssertSuccess();
 
-                string gitPath = GetGitPath();
-                var trace = new NullTrace();
-                var trace2 = new NullTrace2();
-                var processManager = new TestProcessManager();
-                var git = new GitProcess(trace, trace2, processManager, gitPath, repoPath);
-                IGitConfiguration config = git.GetConfiguration();
+            // Use an isolated global config file so tests work even when HOME is not set
+            // to a valid directory (e.g., in package build environments like AUR).
+            using var _ = new GitTestUtilities.EnvVarScope(
+                "GIT_CONFIG_GLOBAL", Path.Combine(workDirPath, ".gitconfig-global"));
 
-                config.Unset(GitConfigurationLevel.Global, "core.foobar");
+            ExecGit(repoPath, workDirPath, "config --global core.foobar alice").AssertSuccess();
+            ExecGit(repoPath, workDirPath, "config --local core.foobar bob").AssertSuccess();
 
-                GitResult globalResult = ExecGit(repoPath, workDirPath, "config --global core.foobar");
-                GitResult localResult = ExecGit(repoPath, workDirPath, "config --local core.foobar");
+            string gitPath = GetGitPath();
+            var trace = new NullTrace();
+            var trace2 = new NullTrace2();
+            var processManager = new TestProcessManager();
+            var git = new GitProcess(trace, trace2, processManager, gitPath, repoPath);
+            IGitConfiguration config = git.GetConfiguration();
 
-                Assert.Equal(string.Empty, globalResult.StandardOutput.Trim());
-                Assert.Equal("bob", localResult.StandardOutput.Trim());
-            }
-            finally
-            {
-                // Cleanup global config changes
-                ExecGit(repoPath, workDirPath, "config --global --unset core.foobar");
-            }
+            config.Unset(GitConfigurationLevel.Global, "core.foobar");
+
+            GitResult globalResult = ExecGit(repoPath, workDirPath, "config --global core.foobar");
+            GitResult localResult = ExecGit(repoPath, workDirPath, "config --local core.foobar");
+
+            Assert.Equal(string.Empty, globalResult.StandardOutput.Trim());
+            Assert.Equal("bob", localResult.StandardOutput.Trim());
         }
 
         [Fact]
         public void GitConfiguration_Unset_Local_UnsetsLocalConfig()
         {
             string repoPath = CreateRepository(out string workDirPath);
 
-            try
-            {
-                ExecGit(repoPath, workDirPath, "config --global core.foobar alice").AssertSuccess();
-                ExecGit(repoPath, workDirPath, "config --local core.foobar bob").AssertSuccess();
+            // Use an isolated global config file so tests work even when HOME is not set
+            // to a valid directory (e.g., in package build environments like AUR).
+            using var _ = new GitTestUtilities.EnvVarScope(
+                "GIT_CONFIG_GLOBAL", Path.Combine(workDirPath, ".gitconfig-global"));
+
+            ExecGit(repoPath, workDirPath, "config --global core.foobar alice").AssertSuccess();
+            ExecGit(repoPath, workDirPath, "config --local core.foobar bob").AssertSuccess();
 
-                string gitPath = GetGitPath();
-                var trace = new NullTrace();
-                var trace2 = new NullTrace2();
-                var processManager = new TestProcessManager();
-                var git = new GitProcess(trace, trace2, processManager, gitPath, repoPath);
-                IGitConfiguration config = git.GetConfiguration();
+            string gitPath = GetGitPath();
+            var trace = new NullTrace();
+            var trace2 = new NullTrace2();
+            var processManager = new TestProcessManager();
+            var git = new GitProcess(trace, trace2, processManager, gitPath, repoPath);
+            IGitConfiguration config = git.GetConfiguration();
 
-                config.Unset(GitConfigurationLevel.Local, "core.foobar");
+            config.Unset(GitConfigurationLevel.Local, "core.foobar");
 
-                GitResult globalResult = ExecGit(repoPath, workDirPath, "config --global core.foobar");
-                GitResult localResult = ExecGit(repoPath, workDirPath, "config --local core.foobar");
+            GitResult globalResult = ExecGit(repoPath, workDirPath, "config --global core.foobar");
+            GitResult localResult = ExecGit(repoPath, workDirPath, "config --local core.foobar");
 
-                Assert.Equal("alice", globalResult.StandardOutput.Trim());
-                Assert.Equal(string.Empty, localResult.StandardOutput.Trim());
-            }
-            finally
-            {
-                // Cleanup global config changes
-                ExecGit(repoPath, workDirPath, "config --global --unset core.foobar");
-            }
+            Assert.Equal("alice", globalResult.StandardOutput.Trim());
+            Assert.Equal(string.Empty, localResult.StandardOutput.Trim());
         }
 
         [Fact]

src/shared/TestInfrastructure/GitTestUtilities.cs

@@ -80,6 +80,11 @@ public static GitResult ExecGit(string repositoryPath, string workingDirectory,
 
             procInfo.Environment["GIT_DIR"] = repositoryPath;
 
+            // Use an isolated global config file in the test's working directory to avoid
+            // failures when HOME is not set to a valid directory (e.g., in package build
+            // environments). This also prevents tests from polluting the user's real global config.
+            procInfo.Environment["GIT_CONFIG_GLOBAL"] = Path.Combine(workingDirectory, ".gitconfig-global");
+
             var proc = ChildProcess.Start(new NullTrace2(), procInfo, Trace2ProcessClass.None);
             if (proc is null)
             {
@@ -109,5 +114,31 @@ public void AssertSuccess()
                 Assert.Equal(0, ExitCode);
             }
         }
+
+        /// <summary>
+        /// Sets an environment variable for the scope of a using block, restoring the original value on dispose.
+        /// </summary>
+        /// <remarks>
+        /// This class modifies the process-level environment, which is shared across all threads.
+        /// To avoid interference, tests using this class should not run concurrently. Tests within
+        /// the same xUnit test class are guaranteed to run serially by default.
+        /// </remarks>
+        public sealed class EnvVarScope : IDisposable
+        {
+            private readonly string _name;
+            private readonly string _previousValue;
+
+            public EnvVarScope(string name, string value)
+            {
+                _name = name;
+                _previousValue = Environment.GetEnvironmentVariable(name);
+                Environment.SetEnvironmentVariable(name, value);
+            }
+
+            public void Dispose()
+            {
+                Environment.SetEnvironmentVariable(_name, _previousValue);
+            }
+        }
     }
 }