Merge: Refactor Metadata to use composition instead of embedding

cmd/submit.go

@@ -28,15 +28,17 @@ type credentials struct {
 	SecretAccessKey string
 }
 
+// A log object can be passed around for use as a logger. It stores logs
+// in memory and can flush the logs to a string when requested.
 type log struct {
 	entries []string
 }
 
 func (l *log) Printf(format string, v ...interface{}) {
 	l.entries = append(l.entries, fmt.Sprintf(format, v...))
-	fmt.Printf(format, v...)
 }
 
+// Text returns a string concatenation of all of the log's entries.
 func (l *log) Text() string {
 	return strings.Join(l.entries, "\n")
 }

metadata/logger.go

@@ -0,0 +1,6 @@
+package metadata
+
+// A Logger represents a mechanism for logging. 🙃
+type Logger interface {
+	Printf(format string, v ...interface{})
+}