Introduce ergonomic API for handling multiple container events

Signed-off-by: Nikhil Benesch <nikhil.benesch@gmail.com>

pkg/progress/noop.go

@@ -27,7 +27,10 @@ func (p *noopWriter) Start(ctx context.Context) error {
 	return nil
 }
 
-func (p *noopWriter) Event(e Event) {
+func (p *noopWriter) Event(Event) {
+}
+
+func (p *noopWriter) Events([]Event) {
 }
 
 func (p *noopWriter) TailMsgf(_ string, _ ...interface{}) {

pkg/progress/plain.go

@@ -40,6 +40,12 @@ func (p *plainWriter) Event(e Event) {
 	fmt.Fprintln(p.out, e.ID, e.Text, e.StatusText)
 }
 
+func (p *plainWriter) Events(events []Event) {
+	for _, e := range events {
+		p.Event(e)
+	}
+}
+
 func (p *plainWriter) TailMsgf(m string, args ...interface{}) {
 	fmt.Fprintln(p.out, append([]interface{}{m}, args...)...)
 }

pkg/progress/tty.go

@@ -95,6 +95,12 @@ func (w *ttyWriter) Event(e Event) {
 	}
 }
 
+func (w *ttyWriter) Events(events []Event) {
+	for _, e := range events {
+		w.Event(e)
+	}
+}
+
 func (w *ttyWriter) TailMsgf(msg string, args ...interface{}) {
 	w.mtx.Lock()
 	defer w.mtx.Unlock()

pkg/progress/writer.go

@@ -31,6 +31,7 @@ type Writer interface {
 	Start(context.Context) error
 	Stop()
 	Event(Event)
+	Events([]Event)
 	TailMsgf(string, ...interface{})
 }