Handle projects from upper directories

Author: edvilme

src/Cli/dotnet/commands/dotnet-sln/add/Program.cs

@@ -100,14 +100,14 @@ private async Task AddProjectsToSolutionAsync(string solutionFileFullPath, IEnum
             foreach (var projectPath in projectPaths)
             {
                 string relativePath = Path.GetRelativePath(Path.GetDirectoryName(solutionFileFullPath), projectPath);
-                // Add fallback solution folder
-                string relativeSolutionFolder = Path.GetDirectoryName(relativePath);
-                // Don't add solution folder if it contains ..
-                if (relativeSolutionFolder.Contains(".."))
+                // If the relative path contains "..", it means the project is outside the solution directory.
+                // In this case, we should not include the ".." in the relative path.
+                if (relativePath.Contains(".."))
                 {
-                    relativeSolutionFolder = string.Empty;
+                    relativePath = relativePath.Substring(relativePath.IndexOf(Path.DirectorySeparatorChar));
                 }
-
+                // Add fallback solution folder
+                string relativeSolutionFolder = Path.GetDirectoryName(relativePath);
                 if (!_inRoot && solutionFolder is null && !string.IsNullOrEmpty(relativeSolutionFolder))
                 {
                     if (relativeSolutionFolder.Split(Path.DirectorySeparatorChar).LastOrDefault() == Path.GetFileNameWithoutExtension(relativePath))