commands: build summary of warnings on build

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

util/logutil/pause.go

@@ -0,0 +1,52 @@
+package logutil
+
+import (
+	"bytes"
+	"io"
+	"sync"
+
+	"github.com/sirupsen/logrus"
+)
+
+func Pause(l *logrus.Logger) func() {
+	// initialize formatter with original terminal settings
+	l.Formatter.Format(logrus.NewEntry(l))
+
+	bw := newBufferedWriter(l.Out)
+	l.SetOutput(bw)
+	return func() {
+		bw.resume()
+	}
+}
+
+type bufferedWriter struct {
+	mu  sync.Mutex
+	buf *bytes.Buffer
+	w   io.Writer
+}
+
+func newBufferedWriter(w io.Writer) *bufferedWriter {
+	return &bufferedWriter{
+		buf: bytes.NewBuffer(nil),
+		w:   w,
+	}
+}
+
+func (bw *bufferedWriter) Write(p []byte) (int, error) {
+	bw.mu.Lock()
+	defer bw.mu.Unlock()
+	if bw.buf == nil {
+		return bw.w.Write(p)
+	}
+	return bw.buf.Write(p)
+}
+
+func (bw *bufferedWriter) resume() {
+	bw.mu.Lock()
+	defer bw.mu.Unlock()
+	if bw.buf == nil {
+		return
+	}
+	io.Copy(bw.w, bw.buf)
+	bw.buf = nil
+}