Cleanup Cmd on ENTRYPOINT instruction

Fixes #5147
Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)

builder/builder.go

@@ -70,6 +70,9 @@ type buildFile struct {
 	// Deprecated, original writer used for ImagePull. To be removed.
 	outOld io.Writer
 	sf     *utils.StreamFormatter
+
+	// cmdSet indicates is CMD was setted in current Dockerfile
+	cmdSet bool
 }
 
 func (b *buildFile) clearTmp(containers map[string]struct{}) {
@@ -306,12 +309,17 @@ func (b *buildFile) CmdCmd(args string) error {
 	if err := b.commit("", b.config.Cmd, fmt.Sprintf("CMD %v", cmd)); err != nil {
 		return err
 	}
+	b.cmdSet = true
 	return nil
 }
 
 func (b *buildFile) CmdEntrypoint(args string) error {
 	entrypoint := b.buildCmdFromJson(args)
 	b.config.Entrypoint = entrypoint
+	// if there is no cmd in current Dockerfile - cleanup cmd
+	if !b.cmdSet {
+		b.config.Cmd = nil
+	}
 	if err := b.commit("", b.config.Cmd, fmt.Sprintf("ENTRYPOINT %v", entrypoint)); err != nil {
 		return err
 	}

integration-cli/docker_cli_build_test.go

@@ -1310,8 +1310,8 @@ func TestBuildEntrypointRunCleanup(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	// Cmd inherited from busybox, maybe will be fixed in #5147
-	if expected := "[/bin/sh]"; res != expected {
+	// Cmd must be cleaned up
+	if expected := "<no value>"; res != expected {
 		t.Fatalf("Cmd %s, expected %s", res, expected)
 	}
 	logDone("build - cleanup cmd after RUN")
@@ -1875,3 +1875,36 @@ func TestBuildFromGIT(t *testing.T) {
 	}
 	logDone("build - build from GIT")
 }
+
+func TestBuildCleanupCmdOnEntrypoint(t *testing.T) {
+	name := "testbuildcmdcleanuponentrypoint"
+	defer deleteImages(name)
+	if _, err := buildImage(name,
+		`FROM scratch
+        CMD ["test"]
+		ENTRYPOINT ["echo"]`,
+		true); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := buildImage(name,
+		fmt.Sprintf(`FROM %s
+		ENTRYPOINT ["cat"]`, name),
+		true); err != nil {
+		t.Fatal(err)
+	}
+	res, err := inspectField(name, "Config.Cmd")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if expected := "<no value>"; res != expected {
+		t.Fatalf("Cmd %s, expected %s", res, expected)
+	}
+	res, err = inspectField(name, "Config.Entrypoint")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if expected := "[cat]"; res != expected {
+		t.Fatalf("Entrypoint %s, expected %s", res, expected)
+	}
+	logDone("build - cleanup cmd on ENTRYPOINT")
+}