images: enable converter to uncompress zstd

Currently uncompress converter only supports gzip. This commit fixes it to
support zstd as well.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>

vendor/github.com/opencontainers/image-spec/specs-go/v1/annotations.go

@@ -53,4 +53,10 @@ const (
 
 	// AnnotationDescription is the annotation key for the human-readable description of the software packaged in the image.
 	AnnotationDescription = "org.opencontainers.image.description"
+
+	// AnnotationBaseImageDigest is the annotation key for the digest of the image's base image.
+	AnnotationBaseImageDigest = "org.opencontainers.image.base.digest"
+
+	// AnnotationBaseImageName is the annotation key for the image reference of the image's base image.
+	AnnotationBaseImageName = "org.opencontainers.image.base.name"
 )

vendor/github.com/opencontainers/image-spec/specs-go/v1/config.go

@@ -89,9 +89,20 @@ type Image struct {
 	// Architecture is the CPU architecture which the binaries in this image are built to run on.
 	Architecture string `json:"architecture"`
 
+	// Variant is the variant of the specified CPU architecture which image binaries are intended to run on.
+	Variant string `json:"variant,omitempty"`
+
 	// OS is the name of the operating system which the image is built to run on.
 	OS string `json:"os"`
 
+	// OSVersion is an optional field specifying the operating system
+	// version, for example on Windows `10.0.14393.1066`.
+	OSVersion string `json:"os.version,omitempty"`
+
+	// OSFeatures is an optional field specifying an array of strings,
+	// each listing a required OS feature (for example on Windows `win32k`).
+	OSFeatures []string `json:"os.features,omitempty"`
+
 	// Config defines the execution parameters which should be used as a base when running a container using the image.
 	Config ImageConfig `json:"config,omitempty"`
 

vendor/github.com/opencontainers/image-spec/specs-go/v1/mediatype.go

@@ -34,6 +34,10 @@ const (
 	// referenced by the manifest.
 	MediaTypeImageLayerGzip = "application/vnd.oci.image.layer.v1.tar+gzip"
 
+	// MediaTypeImageLayerZstd is the media type used for zstd compressed
+	// layers referenced by the manifest.
+	MediaTypeImageLayerZstd = "application/vnd.oci.image.layer.v1.tar+zstd"
+
 	// MediaTypeImageLayerNonDistributable is the media type for layers referenced by
 	// the manifest but with distribution restrictions.
 	MediaTypeImageLayerNonDistributable = "application/vnd.oci.image.layer.nondistributable.v1.tar"
@@ -43,6 +47,11 @@ const (
 	// restrictions.
 	MediaTypeImageLayerNonDistributableGzip = "application/vnd.oci.image.layer.nondistributable.v1.tar+gzip"
 
+	// MediaTypeImageLayerNonDistributableZstd is the media type for zstd
+	// compressed layers referenced by the manifest but with distribution
+	// restrictions.
+	MediaTypeImageLayerNonDistributableZstd = "application/vnd.oci.image.layer.nondistributable.v1.tar+zstd"
+
 	// MediaTypeImageConfig specifies the media type for the image configuration.
 	MediaTypeImageConfig = "application/vnd.oci.image.config.v1+json"
 )

vendor/github.com/opencontainers/image-spec/specs-go/version.go

@@ -25,7 +25,7 @@ const (
 	VersionPatch = 1
 
 	// VersionDev indicates development branch. Releases will be empty string.
-	VersionDev = ""
+	VersionDev = "-dev"
 )
 
 // Version is the specification version that the package types support.

vendor/modules.txt

@@ -302,7 +302,7 @@ github.com/modern-go/reflect2
 ## explicit
 github.com/opencontainers/go-digest
 github.com/opencontainers/go-digest/digestset
-# github.com/opencontainers/image-spec v1.0.1
+# github.com/opencontainers/image-spec v1.0.2-0.20210819154149-5ad6f50d6283
 ## explicit
 github.com/opencontainers/image-spec/identity
 github.com/opencontainers/image-spec/specs-go