Move garbage collect code into storage package

Signed-off-by: Richard Scothern <richard.scothern@docker.com>

docs/root.go

@@ -1,7 +1,14 @@
 package registry
 
 import (
+	"fmt"
+	"os"
+
+	"github.com/docker/distribution/context"
+	"github.com/docker/distribution/registry/storage"
+	"github.com/docker/distribution/registry/storage/driver/factory"
 	"github.com/docker/distribution/version"
+	"github.com/docker/libtrust"
 	"github.com/spf13/cobra"
 )
 
@@ -10,6 +17,7 @@ var showVersion bool
 func init() {
 	RootCmd.AddCommand(ServeCmd)
 	RootCmd.AddCommand(GCCmd)
+	GCCmd.Flags().BoolVarP(&dryRun, "dry-run", "d", false, "do everything except remove the blobs")
 	RootCmd.Flags().BoolVarP(&showVersion, "version", "v", false, "show the version and exit")
 }
 
@@ -26,3 +34,51 @@ var RootCmd = &cobra.Command{
 		cmd.Usage()
 	},
 }
+
+var dryRun bool
+
+// GCCmd is the cobra command that corresponds to the garbage-collect subcommand
+var GCCmd = &cobra.Command{
+	Use:   "garbage-collect <config>",
+	Short: "`garbage-collect` deletes layers not referenced by any manifests",
+	Long:  "`garbage-collect` deletes layers not referenced by any manifests",
+	Run: func(cmd *cobra.Command, args []string) {
+		config, err := resolveConfiguration(args)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "configuration error: %v\n", err)
+			cmd.Usage()
+			os.Exit(1)
+		}
+
+		driver, err := factory.Create(config.Storage.Type(), config.Storage.Parameters())
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "failed to construct %s driver: %v", config.Storage.Type(), err)
+			os.Exit(1)
+		}
+
+		ctx := context.Background()
+		ctx, err = configureLogging(ctx, config)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "unable to configure logging with config: %s", err)
+			os.Exit(1)
+		}
+
+		k, err := libtrust.GenerateECP256PrivateKey()
+		if err != nil {
+			fmt.Fprint(os.Stderr, err)
+			os.Exit(1)
+		}
+
+		registry, err := storage.NewRegistry(ctx, driver, storage.DisableSchema1Signatures, storage.Schema1SigningKey(k))
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "failed to construct registry: %v", err)
+			os.Exit(1)
+		}
+
+		err = storage.MarkAndSweep(ctx, driver, registry, dryRun)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "failed to garbage collect: %v", err)
+			os.Exit(1)
+		}
+	},
+}