Add support for Fulcio and Rekor, and --sign-by-sigstore=param-file

(skopeo copy) and (skopeo sync) now support --sign-by-sigstore=param-file,
using the containers-sigstore-signing-params.yaml(5) file format.

That notably adds support for Fulcio and Rekor signing.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/github.com/go-openapi/runtime/yamlpc/yaml.go

@@ -0,0 +1,40 @@
+// Copyright 2015 go-swagger maintainers
+//
+// 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 yamlpc
+
+import (
+	"io"
+
+	"github.com/go-openapi/runtime"
+
+	"gopkg.in/yaml.v2"
+)
+
+// YAMLConsumer creates a consumer for yaml data
+func YAMLConsumer() runtime.Consumer {
+	return runtime.ConsumerFunc(func(r io.Reader, v interface{}) error {
+		dec := yaml.NewDecoder(r)
+		return dec.Decode(v)
+	})
+}
+
+// YAMLProducer creates a producer for yaml data
+func YAMLProducer() runtime.Producer {
+	return runtime.ProducerFunc(func(w io.Writer, v interface{}) error {
+		enc := yaml.NewEncoder(w)
+		defer enc.Close()
+		return enc.Encode(v)
+	})
+}