Fix parsing values which starts with dash, but has whitespace inside.

this is required when your option can accept command line arguments to other applications.

See dotnet/BenchmarkDotNet#2320 (comment) for example of parsing issues

src/CommandLine/Core/Tokenizer.cs

@@ -28,7 +28,7 @@ public static Result<IEnumerable<Token>, Error> Tokenize(
  Action<Error> onError = errors.Add;
 
  var tokens = (from arg in arguments
- from token in !arg.StartsWith("-", StringComparison.Ordinal)
+ from token in (!arg.StartsWith("-", StringComparison.Ordinal) || arg.Contains(" "))
  ? new[] { Token.Value(arg) }
  : arg.StartsWith("--", StringComparison.Ordinal)
  ? TokenizeLongName(arg, onError)

tests/CommandLine.Tests/Unit/ParserTests.cs

@@ -163,6 +163,27 @@ public void Parse_options_with_double_dash()
  // Teardown
  }
 
+ [Fact]
+ public void Parse_options_with_whitespace_and_double_dash()
+ {
+ // Fixture setup
+ var expectedOptions = new Simple_Options
+ {
+ StringValue = "--astring value",
+ IntSequence = Enumerable.Empty<int>(),
+ };
+ var sut = new Parser();
+
+ // Exercize system
+ var result =
+ sut.ParseArguments<Simple_Options>(
+ new[] { "--stringvalue", "--astring value" });
+
+ // Verify outcome
+ ((Parsed<Simple_Options>)result).Value.Should().BeEquivalentTo(expectedOptions);
+ // Teardown
+ }
+
  [Fact]
  public void Parse_options_with_repeated_value_in_values_sequence_and_option()
  {