Change path breakout detection logic in archive package

Fixes #9375

Signed-off-by: Alexandr Morozov <lk4d4@docker.com>

integration-cli/docker_cli_cp_test.go

@@ -478,3 +478,41 @@ func TestCpVolumePath(t *testing.T) {
 
 	logDone("cp - volume path")
 }
+
+func TestCpToDot(t *testing.T) {
+	out, exitCode, err := dockerCmd(t, "run", "-d", "busybox", "/bin/sh", "-c", "echo lololol > /test")
+	if err != nil || exitCode != 0 {
+		t.Fatal("failed to create a container", out, err)
+	}
+
+	cleanedContainerID := stripTrailingCharacters(out)
+	defer deleteContainer(cleanedContainerID)
+
+	out, _, err = dockerCmd(t, "wait", cleanedContainerID)
+	if err != nil || stripTrailingCharacters(out) != "0" {
+		t.Fatal("failed to set up container", out, err)
+	}
+
+	tmpdir, err := ioutil.TempDir("", "docker-integration")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpdir)
+	cwd, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.Chdir(cwd)
+	if err := os.Chdir(tmpdir); err != nil {
+		t.Fatal(err)
+	}
+	_, _, err = dockerCmd(t, "cp", cleanedContainerID+":/test", ".")
+	if err != nil {
+		t.Fatalf("couldn't docker cp to \".\" path: %s", err)
+	}
+	content, err := ioutil.ReadFile("./test")
+	if string(content) != "lololol\n" {
+		t.Fatal("Wrong content in copied file %q, should be %q", content, "lololol\n")
+	}
+	logDone("cp - to dot path")
+}