special case http errors if the first error is not wrapped

Signed-off-by: Scott Nichols <n3wscott@chainguard.dev>

v2/protocol/http/protocol.go

@@ -157,7 +157,14 @@ func (p *Protocol) Send(ctx context.Context, m binding.Message, transformers ...
 				buf := new(bytes.Buffer)
 				buf.ReadFrom(message.BodyReader)
 				errorStr := buf.String()
-				err = NewResult(res.StatusCode, "%w: %s", err, errorStr)
+				// If the error is not wrapped, then append the original error string.
+				if og, ok := err.(*Result); ok {
+					og.Format = og.Format + "%s"
+					og.Args = append(og.Args, errorStr)
+					err = og
+				} else {
+					err = NewResult(res.StatusCode, "%w: %s", err, errorStr)
+				}
 			}
 		}
 	}