bake: initial implementation

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

util/progress/multiwriter.go

@@ -0,0 +1,96 @@
+package progress
+
+import (
+	"context"
+	"strings"
+
+	"github.com/moby/buildkit/client"
+	"golang.org/x/sync/errgroup"
+)
+
+type MultiWriter struct {
+	w  Writer
+	eg *errgroup.Group
+}
+
+func (mw *MultiWriter) WithPrefix(pfx string, force bool) Writer {
+	in := make(chan *client.SolveStatus)
+	out := mw.w.Status()
+	p := &prefixed{
+		main: mw.w,
+		in:   in,
+	}
+	mw.eg.Go(func() error {
+		for {
+			select {
+			case v, ok := <-in:
+				if ok {
+					if force {
+						for _, v := range v.Vertexes {
+							v.Name = addPrefix(pfx, v.Name)
+						}
+					}
+					out <- v
+				} else {
+					return nil
+				}
+			case <-mw.Done():
+				return mw.Err()
+			}
+		}
+	})
+	return p
+}
+
+func (mw *MultiWriter) Done() <-chan struct{} {
+	return mw.w.Done()
+}
+
+func (mw *MultiWriter) Err() error {
+	return mw.w.Err()
+}
+
+func (mw *MultiWriter) Status() chan *client.SolveStatus {
+	return nil
+}
+
+type prefixed struct {
+	main Writer
+	in   chan *client.SolveStatus
+}
+
+func (p *prefixed) Done() <-chan struct{} {
+	return p.main.Done()
+}
+
+func (p *prefixed) Err() error {
+	return p.main.Err()
+}
+
+func (p *prefixed) Status() chan *client.SolveStatus {
+	return p.in
+}
+
+func NewMultiWriter(pw Writer) *MultiWriter {
+	if pw == nil {
+		return nil
+	}
+	eg, _ := errgroup.WithContext(context.TODO())
+
+	go func() {
+		eg.Wait()
+		close(pw.Status())
+	}()
+
+	return &MultiWriter{
+		w:  pw,
+		eg: eg,
+	}
+}
+
+func addPrefix(pfx, name string) string {
+	if strings.HasPrefix(name, "[") {
+		return "[" + pfx + " " + name[1:]
+	}
+	return "[" + pfx + "] " + name
+}