vendor: revendor github.com/opencontainers/image-tools@da84dc9dddc823a32f543e60323f841d12429c51

This requires re-vendoring a bunch of other things (as well as the old
Sirupsen/logrus path), the relevant commits being:

* github.com/xeipuuv/gojsonschema@0c8571ac0ce161a5feb57375a9cdf148c98c0f70
* github.com/xeipuuv/gojsonpointer@6fe8760cad3569743d51ddbb243b26f8456742dc
* github.com/xeipuuv/gojsonreference@e02fc20de94c78484cd5ffb007f8af96be030a45
* go4.org@034d17a462f7b2dcd1a4a73553ec5357ff6e6c6e

Signed-off-by: Aleksa Sarai <asarai@suse.de>

vendor/github.com/opencontainers/image-tools/image/autodetect.go

@@ -0,0 +1,109 @@
+// Copyright 2016 The Linux Foundation
+//
+// 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 image
+
+import (
+	"encoding/json"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"os"
+
+	"github.com/opencontainers/image-spec/schema"
+	"github.com/pkg/errors"
+)
+
+// supported autodetection types
+const (
+	TypeImageLayout = "imageLayout"
+	TypeImage       = "image"
+	TypeManifest    = "manifest"
+	TypeImageIndex  = "imageIndex"
+	TypeConfig      = "config"
+)
+
+// Autodetect detects the validation type for the given path
+// or an error if the validation type could not be resolved.
+func Autodetect(path string) (string, error) {
+	fi, err := os.Stat(path)
+	if err != nil {
+		return "", errors.Wrapf(err, "unable to access path") // err from os.Stat includes path name
+	}
+
+	if fi.IsDir() {
+		return TypeImageLayout, nil
+	}
+
+	f, err := os.Open(path)
+	if err != nil {
+		return "", errors.Wrap(err, "unable to open file") // os.Open includes the filename
+	}
+	defer f.Close()
+
+	buf, err := ioutil.ReadAll(io.LimitReader(f, 512)) // read some initial bytes to detect content
+	if err != nil {
+		return "", errors.Wrap(err, "unable to read")
+	}
+
+	mimeType := http.DetectContentType(buf)
+
+	switch mimeType {
+	case "application/x-gzip", "application/octet-stream":
+		return TypeImage, nil
+
+	case "text/plain; charset=utf-8":
+		// might be a JSON file, will be handled below
+
+	default:
+		return "", errors.New("unknown file type")
+	}
+
+	if _, err := f.Seek(0, io.SeekStart); err != nil {
+		return "", errors.Wrap(err, "unable to seek")
+	}
+
+	header := struct {
+		SchemaVersion int         `json:"schemaVersion"`
+		MediaType     string      `json:"mediaType"`
+		Config        interface{} `json:"config"`
+	}{}
+
+	if err := json.NewDecoder(f).Decode(&header); err != nil {
+		if _, errSeek := f.Seek(0, io.SeekStart); errSeek != nil {
+			return "", errors.Wrap(err, "unable to seek")
+		}
+
+		e := errors.Wrap(
+			schema.WrapSyntaxError(f, err),
+			"unable to parse JSON",
+		)
+
+		return "", e
+	}
+
+	switch {
+	case header.MediaType == string(schema.ValidatorMediaTypeManifest):
+		return TypeManifest, nil
+
+	case header.MediaType == string(schema.ValidatorMediaTypeImageIndex):
+		return TypeImageIndex, nil
+
+	case header.MediaType == "" && header.SchemaVersion == 0 && header.Config != nil:
+		// config files don't have mediaType/schemaVersion header
+		return TypeConfig, nil
+	}
+
+	return "", errors.New("unknown media type")
+}