build: add experimental --no-console flag to support non-tty human-readable output with buildkit

Unfortunately, this is for now the only way to see the output of RUN commands when using buildkit.
It is equivalent to `DOCKER_BUILDKIT=1 docker build . 2>&1 | cat`

Signed-off-by: Tibor Vass <tibor@docker.com>

cli/command/image/build.go

@@ -57,6 +57,7 @@ type buildOptions struct {
 	isolation      string
 	quiet          bool
 	noCache        bool
+	noConsole      bool
 	rm             bool
 	forceRm        bool
 	pull           bool
@@ -151,6 +152,9 @@ func NewBuildCommand(dockerCli command.Cli) *cobra.Command {
 	flags.SetAnnotation("stream", "experimental", nil)
 	flags.SetAnnotation("stream", "version", []string{"1.31"})
 
+	flags.BoolVar(&options.noConsole, "no-console", false, "Show non-console output (with buildkit only)")
+	flags.SetAnnotation("no-console", "experimental", nil)
+	flags.SetAnnotation("no-console", "version", []string{"1.38"})
 	return cmd
 }
 

cli/command/image/build_buildkit.go

@@ -212,23 +212,15 @@ func runBuildBuildKit(dockerCli command.Cli, options buildOptions) error {
 		ssArr := []*client.SolveStatus{}
 
 		displayStatus := func(displayCh chan *client.SolveStatus) {
-			if c, err := console.ConsoleFromFile(os.Stderr); err == nil {
-				// not using shared context to not disrupt display but let is finish reporting errors
-				eg.Go(func() error {
-					return progressui.DisplaySolveStatus(context.TODO(), c, displayCh)
-				})
-			} else {
-				// read from t.displayCh and send json to Stderr
-				eg.Go(func() error {
-					enc := json.NewEncoder(os.Stderr)
-					for ss := range displayCh {
-						if err := enc.Encode(ss); err != nil {
-							return err
-						}
-					}
-					return nil
-				})
+			var c console.Console
+			out := os.Stderr
+			if cons, err := console.ConsoleFromFile(out); err == nil && !options.noConsole {
+				c = cons
 			}
+			// not using shared context to not disrupt display but let is finish reporting errors
+			eg.Go(func() error {
+				return progressui.DisplaySolveStatus(context.TODO(), c, out, displayCh)
+			})
 		}
 
 		if options.quiet {