Fix dotnet reference add/remove failing when no --project is specified

src/Cli/dotnet/Commands/Reference/Add/ReferenceAddCommand.cs

@@ -17,7 +17,7 @@ internal sealed class ReferenceAddCommand : CommandBase<ReferenceAddCommandDefin
     public ReferenceAddCommand(ParseResult parseResult)
         : base(parseResult)
     {
-        _fileOrDirectory = Definition.GetFileOrDirectory(parseResult);
+        _fileOrDirectory = Definition.GetFileOrDirectory(parseResult) ?? Directory.GetCurrentDirectory();
     }
 
     public override int Execute()

src/Cli/dotnet/Commands/Reference/Remove/ReferenceRemoveCommand.cs

@@ -17,7 +17,7 @@ internal sealed class ReferenceRemoveCommand : CommandBase<ReferenceRemoveComman
     public ReferenceRemoveCommand(ParseResult parseResult)
         : base(parseResult)
     {
-        _fileOrDirectory = Definition.GetFileOrDirectory(parseResult);
+        _fileOrDirectory = Definition.GetFileOrDirectory(parseResult) ?? Directory.GetCurrentDirectory();
         _arguments = parseResult.GetValue(Definition.ProjectPathArgument).ToList().AsReadOnly();
 
         if (_arguments.Count == 0)

test/dotnet.Tests/CommandTests/Reference/Add/GivenDotnetAddReference.cs

@@ -713,6 +713,22 @@ public void WhenDirectoryContainingProjectIsGivenReferenceIsAdded()
             result.StdErr.Should().BeEmpty();
         }
 
+        [Fact]
+        public void WhenNoProjectIsSpecifiedItUsesCurrentDirectory()
+        {
+            var setup = Setup();
+            var lib = NewLibWithFrameworks(dir: setup.TestRoot);
+
+            // Reproduces: dotnet reference add ../ValidRef/ValidRef.csproj
+            // where the current directory contains a project (no --project argument needed)
+            var result = new DotnetCommand(Log, "reference", "add")
+                    .WithWorkingDirectory(lib.Path)
+                    .Execute(setup.ValidRefCsprojPath);
+
+            result.Should().Pass();
+            result.StdErr.Should().BeEmpty();
+        }
+
         [Fact]
         public void WhenDirectoryContainsNoProjectsItCancelsWholeOperation()
         {

test/dotnet.Tests/CommandTests/Reference/Remove/GivenDotnetRemoveP2P.cs

@@ -581,5 +581,22 @@ public void WhenDirectoryContainsMultipleProjectsItCancelsWholeOperation()
             result.StdOut.Should().BeVisuallyEquivalentToIfNotLocalized("");
             result.StdErr.Should().Be(string.Format(CliStrings.MoreThanOneProjectInDirectory, Path.Combine(setup.TestRoot, reference)));
         }
+
+        [Fact]
+        public void WhenNoProjectIsSpecifiedItUsesCurrentDirectory()
+        {
+            var setup = Setup();
+            var lib = NewLibWithFrameworks(dir: setup.TestRoot);
+            var libref = AddLibRef(setup, lib);
+
+            // Reproduces: dotnet reference remove ../Lib/Lib.csproj
+            // where the current directory contains a project (no --project argument needed)
+            var result = new DotnetCommand(Log, "reference", "remove")
+                    .WithWorkingDirectory(lib.Path)
+                    .Execute(libref.CsProjPath);
+
+            result.Should().Pass();
+            result.StdErr.Should().BeEmpty();
+        }
     }
 }