Add IStream::isStdOut

src/catch2/internal/catch_stream.cpp

@@ -99,6 +99,7 @@ namespace Detail {
 
         public: // IStream
             std::ostream& stream() const override { return m_os; }
+            bool isStdout() const override { return true; }
         };
 
         ///////////////////////////////////////////////////////////////////////////

src/catch2/internal/catch_stream.hpp

@@ -25,6 +25,9 @@ namespace Catch {
     struct IStream {
         virtual ~IStream(); // = default
         virtual std::ostream& stream() const = 0;
+        // Win32 colour supports requires us to identify whether a stream
+        // is backed by stdout (so we can colour it) or not (and we can't).
+        virtual bool isStdout() const { return false;  }
     };
 
     auto makeStream( std::string const& filename ) -> Detail::unique_ptr<IStream const>;