Add more commentary to minNonLiteralBlockSize.
diff --git a/encode.go b/encode.go
index c57a0f2..0fc1cc9 100644
--- a/encode.go
+++ b/encode.go
@@ -160,6 +160,9 @@
//
// The C++ code doesn't use this exact threshold, but it could, as discussed at
// https://groups.google.com/d/topic/snappy-compression/oGbhsdIJSJ8/discussion
+// The difference between Go (2+inputMargin) and C++ (inputMargin) is purely an
+// optimization. It should not affect the encoded form. This is tested by
+// TestSameEncodingAsCppShortCopies.
const minNonLiteralBlockSize = 1 + 1 + inputMargin
func hash(u, shift uint32) uint32 {
