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/errors/parsing.go

@@ -0,0 +1,78 @@
+// 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 errors
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// ParseError represents a parsing error
+type ParseError struct {
+	code    int32
+	Name    string
+	In      string
+	Value   string
+	Reason  error
+	message string
+}
+
+func (e *ParseError) Error() string {
+	return e.message
+}
+
+// Code returns the http status code for this error
+func (e *ParseError) Code() int32 {
+	return e.code
+}
+
+// MarshalJSON implements the JSON encoding interface
+func (e ParseError) MarshalJSON() ([]byte, error) {
+	var reason string
+	if e.Reason != nil {
+		reason = e.Reason.Error()
+	}
+	return json.Marshal(map[string]interface{}{
+		"code":    e.code,
+		"message": e.message,
+		"in":      e.In,
+		"name":    e.Name,
+		"value":   e.Value,
+		"reason":  reason,
+	})
+}
+
+const (
+	parseErrorTemplContent     = `parsing %s %s from %q failed, because %s`
+	parseErrorTemplContentNoIn = `parsing %s from %q failed, because %s`
+)
+
+// NewParseError creates a new parse error
+func NewParseError(name, in, value string, reason error) *ParseError {
+	var msg string
+	if in == "" {
+		msg = fmt.Sprintf(parseErrorTemplContentNoIn, name, value, reason)
+	} else {
+		msg = fmt.Sprintf(parseErrorTemplContent, name, in, value, reason)
+	}
+	return &ParseError{
+		code:    400,
+		Name:    name,
+		In:      in,
+		Value:   value,
+		Reason:  reason,
+		message: msg,
+	}
+}