Set content labels based on content type

Give control of the content labeling process for children to
the client. This allows the client to control the names
associated with the labels and filter out labels.

Signed-off-by: Derek McGowan <derek@mcg.dev>

client_opts.go

@@ -23,6 +23,7 @@ import (
 	"github.com/containerd/containerd/platforms"
 	"github.com/containerd/containerd/remotes"
 	"github.com/containerd/containerd/snapshots"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 
 	"google.golang.org/grpc"
 )
@@ -132,14 +133,6 @@ func WithPullUnpack(_ *Client, c *RemoteContext) error {
 	return nil
 }
 
-// WithDiscardContent is used to allow GC to clean layers up from
-// the content store after successfully unpacking these contents to
-// the snapshotter.
-func WithDiscardContent(_ *Client, c *RemoteContext) error {
-	c.DiscardContent = true
-	return nil
-}
-
 // WithUnpackOpts is used to add unpack options to the unpacker.
 func WithUnpackOpts(opts []UnpackOpt) RemoteOpt {
 	return func(_ *Client, c *RemoteContext) error {
@@ -183,6 +176,18 @@ func WithPullLabels(labels map[string]string) RemoteOpt {
 	}
 }
 
+// WithChildLabelMap sets the map function used to define the labels set
+// on referenced child content in the content store. This can be used
+// to overwrite the default GC labels or filter which labels get set
+// for content.
+// The default is `images.ChildGCLabels`.
+func WithChildLabelMap(fn func(ocispec.Descriptor) []string) RemoteOpt {
+	return func(_ *Client, c *RemoteContext) error {
+		c.ChildLabelMap = fn
+		return nil
+	}
+}
+
 // WithSchema1Conversion is used to convert Docker registry schema 1
 // manifests to oci manifests on pull. Without this option schema 1
 // manifests will return a not supported error.