Improve docker load output in bazel build

Fixes #416

Currently we add the streaming of son messages.
It would be even better to stream them with the
`isTerminal` flag set but it seems to fail on some
setup.

Signed-off-by: David Gageot <[email protected]>

Author: dgageot

pkg/skaffold/build/bazel.go

@@ -20,12 +20,12 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"strings"
 
+	"github.com/GoogleContainerTools/skaffold/pkg/skaffold/docker"
 	"github.com/GoogleContainerTools/skaffold/pkg/skaffold/schema/v1alpha2"
 	"github.com/pkg/errors"
 )
@@ -43,21 +43,23 @@ func (l *LocalBuilder) buildBazel(ctx context.Context, out io.Writer, a *v1alpha
 	tarPath := strings.TrimPrefix(a.BazelArtifact.BuildTarget, "//:")
 	//TODO(r2d4): strip off trailing .tar, even worse
 	imageTag := strings.TrimSuffix(tarPath, ".tar")
+
 	imageTar, err := os.Open(filepath.Join(a.Workspace, "bazel-bin", tarPath))
 	if err != nil {
 		return "", errors.Wrap(err, "opening image tarball")
 	}
 	defer imageTar.Close()
+
 	resp, err := l.api.ImageLoad(ctx, imageTar, false)
 	if err != nil {
 		return "", errors.Wrap(err, "loading image into docker daemon")
 	}
 	defer resp.Body.Close()
-	respStr, err := ioutil.ReadAll(resp.Body)
+
+	err = docker.StreamDockerMessages(out, resp.Body)
 	if err != nil {
 		return "", errors.Wrap(err, "reading from image load response")
 	}
-	out.Write(respStr)
 
 	return fmt.Sprintf("bazel:%s", imageTag), nil
 }

pkg/skaffold/docker/image.go

@@ -78,11 +78,11 @@ func RunBuild(ctx context.Context, cli DockerAPIClient, opts *BuildOptions) erro
 		return errors.Wrap(err, "docker build")
 	}
 	defer resp.Body.Close()
-	return streamDockerMessages(opts.BuildBuf, resp.Body)
+	return StreamDockerMessages(opts.BuildBuf, resp.Body)
 }
 
 // TODO(@r2d4): Make this output much better, this is the bare minimum
-func streamDockerMessages(dst io.Writer, src io.Reader) error {
+func StreamDockerMessages(dst io.Writer, src io.Reader) error {
 	fd, _ := term.GetFdInfo(dst)
 	return jsonmessage.DisplayJSONMessagesStream(src, dst, fd, false, nil)
 }
@@ -99,7 +99,7 @@ func RunPush(ctx context.Context, cli DockerAPIClient, ref string, out io.Writer
 		return errors.Wrap(err, "pushing image to repository")
 	}
 	defer rc.Close()
-	return streamDockerMessages(out, rc)
+	return StreamDockerMessages(out, rc)
 }
 
 func AddTag(src, target string) error {