feat: return error when header flags used on oci layout (#841)

Signed-off-by: Billy Zha <jinzha1@microsoft.com>

cmd/oras/internal/option/target.go

@@ -17,6 +17,7 @@ package option
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"os"
 	"strings"
@@ -86,6 +87,9 @@ func (opts *Target) Parse() error {
 	switch {
 	case opts.isOCILayout:
 		opts.Type = TargetTypeOCILayout
+		if len(opts.headerFlags) != 0 {
+			return errors.New("custom header flags cannot be used on an OCI image layout target")
+		}
 		return nil
 	default:
 		opts.Type = TargetTypeRemote

test/e2e/suite/command/customer_header.go

@@ -0,0 +1,31 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package command
+
+import (
+	. "github.com/onsi/ginkgo/v2"
+	. "oras.land/oras/test/e2e/internal/utils"
+)
+
+var _ = Describe("OCI image layout users:", func() {
+	When("custom header is provided", func() {
+		It("should fail attach", func() {
+			ORAS("attach", ".:test", "-a", "test=true", "--artifact-type", "doc/example", "--oci-layout", "-H=foo:bar").
+				WithWorkDir(GinkgoT().TempDir()).
+				ExpectFailure().
+				MatchErrKeyWords("custom header").
+				Exec()
+		})
+	})
+})