Fix crash when git branch config has a duplicate key

src/Fallout.Build/VCS/GitRepository.cs

@@ -74,8 +74,10 @@ private static (string Name, string Branch) GetRemoteNameAndBranch(AbsolutePath
             .SkipWhile(x => x != $"[branch {branch.DoubleQuote()}]")
             .Skip(1)
             .TakeWhile(x => !x.StartsWith("["))
-            .Select(x => x.Split('='))
-            .ToDictionary(x => x.ElementAt(0).Trim(), x => x.ElementAt(1).Trim());
+            .Where(x => x.Contains('='))
+            .Select(x => x.Split('=', 2))
+            .GroupBy(x => x[0].Trim(), x => x[1].Trim())
+            .ToDictionary(x => x.Key, x => x.Last());
         return data.TryGetValue("remote", out var remote) && data.TryGetValue("merge", out var merge)
             ? (remote, merge.TrimStart("refs/heads/"))
             : (null, null);

tests/Fallout.Build.Tests/GitRepositoryTest.cs

@@ -56,4 +56,66 @@ public void FromDirectoryTest()
         repository.Commit.Should().NotBeNullOrEmpty();
         repository.Tags.Should().NotBeNull();
     }
+
+    [Fact]
+    public void FromDirectoryTest_WithDuplicateVscodeMergeBaseKey_DoesNotThrow()
+    {
+        // VS Code's Git extension is known to append a duplicate `vscode-merge-base` line to the
+        // `[branch "<name>"]` section instead of updating it in place, which used to crash
+        // GetRemoteNameAndBranch's ToDictionary call. See regression report for details.
+        var directory = Path.Combine(Path.GetTempPath(), Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(directory);
+
+        try
+        {
+            RunGit(directory, "init --quiet --initial-branch=main");
+            RunGit(directory, "config user.email test@example.com");
+            RunGit(directory, "config user.name Test");
+            File.WriteAllText(Path.Combine(directory, "file.txt"), "content");
+            RunGit(directory, "add file.txt");
+            RunGit(directory, "commit --quiet -m initial");
+            RunGit(directory, "remote add origin https://github.com/nuke-build/nuke.git");
+            RunGit(directory, "config branch.main.remote origin");
+            RunGit(directory, "config branch.main.merge refs/heads/main");
+
+            var configPath = Path.Combine(directory, ".git", "config");
+            File.AppendAllText(
+                configPath,
+                "\tvscode-merge-base = origin/main" + Environment.NewLine +
+                "\tvscode-merge-base = origin/main" + Environment.NewLine);
+
+            var repository = GitRepository.FromLocalDirectory(directory);
+
+            repository.Branch.Should().Be("main");
+            repository.Identifier.Should().Be("nuke-build/nuke");
+        }
+        finally
+        {
+            ForceDeleteDirectory(directory);
+        }
+    }
+
+    private static void ForceDeleteDirectory(string directory)
+    {
+        // Git marks object files read-only, which trips up Directory.Delete on Windows.
+        foreach (var file in Directory.GetFiles(directory, "*", SearchOption.AllDirectories))
+            File.SetAttributes(file, FileAttributes.Normal);
+
+        Directory.Delete(directory, recursive: true);
+    }
+
+    private static void RunGit(string workingDirectory, string arguments)
+    {
+        var startInfo = new System.Diagnostics.ProcessStartInfo("git", arguments)
+        {
+            WorkingDirectory = workingDirectory,
+            RedirectStandardOutput = true,
+            RedirectStandardError = true,
+            UseShellExecute = false
+        };
+
+        using var process = System.Diagnostics.Process.Start(startInfo).NotNull();
+        process.WaitForExit();
+        process.ExitCode.Should().Be(0, process.StandardError.ReadToEnd());
+    }
 }