daemon: update: check len inside public function

Signed-off-by: Antonio Murdaca <runcom@redhat.com>

builder/dockerfile/internals.go

@@ -527,11 +527,9 @@ func (b *Builder) create() (string, error) {
 	b.tmpContainers[c.ID] = struct{}{}
 	fmt.Fprintf(b.Stdout, " ---> Running in %s\n", stringid.TruncateID(c.ID))
 
-	if len(config.Cmd) > 0 {
-		// override the entry point that may have been picked up from the base image
-		if err := b.docker.ContainerUpdateCmdOnBuild(c.ID, config.Cmd); err != nil {
-			return "", err
-		}
+	// override the entry point that may have been picked up from the base image
+	if err := b.docker.ContainerUpdateCmdOnBuild(c.ID, config.Cmd); err != nil {
+		return "", err
 	}
 
 	return c.ID, nil

daemon/update.go

@@ -25,6 +25,9 @@ func (daemon *Daemon) ContainerUpdate(name string, hostConfig *container.HostCon
 
 // ContainerUpdateCmdOnBuild updates Path and Args for the container with ID cID.
 func (daemon *Daemon) ContainerUpdateCmdOnBuild(cID string, cmd []string) error {
+	if len(cmd) == 0 {
+		return nil
+	}
 	c, err := daemon.GetContainer(cID)
 	if err != nil {
 		return err

registry/registry_test.go

@@ -171,7 +171,7 @@ func TestGetRemoteImageJSON(t *testing.T) {
 		t.Fatal(err)
 	}
 	assertEqual(t, size, int64(154), "Expected size 154")
-	if len(json) <= 0 {
+	if len(json) == 0 {
 		t.Fatal("Expected non-empty json")
 	}