Add a command to squash images.

cmd/crane/cmd/squash.go

@@ -0,0 +1,65 @@
+// Copyright 2018 Google LLC All Rights Reserved.
+//
+// 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 cmd
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/google/go-containerregistry/pkg/crane"
+	"github.com/google/go-containerregistry/pkg/v1/mutate"
+	"github.com/spf13/cobra"
+)
+
+func init() { Root.AddCommand(NewCmdSquash()) }
+
+// NewCmdSquash creates a new cobra.Command for the squash subcommand.
+func NewCmdSquash() *cobra.Command {
+	var orig, squashed string
+
+	squashCmd := &cobra.Command{
+		Use:   "squash",
+		Short: "Squash an image onto a new base image",
+		Args:  cobra.NoArgs,
+		Run: func(*cobra.Command, []string) {
+			origImg, err := crane.Pull(orig, options...)
+			if err != nil {
+				log.Fatalf("pulling %s: %v", orig, err)
+			}
+
+			img, err := mutate.Squash(origImg)
+			if err != nil {
+				log.Fatalf("squashing: %v", err)
+			}
+
+			if err := crane.Push(img, squashed, options...); err != nil {
+				log.Fatalf("pushing %s: %v", squashed, err)
+			}
+
+			digest, err := img.Digest()
+			if err != nil {
+				log.Fatalf("digesting squashed: %v", err)
+			}
+			fmt.Println(digest.String())
+		},
+	}
+	squashCmd.Flags().StringVarP(&orig, "original", "", "", "Original image to squash")
+	squashCmd.Flags().StringVarP(&squashed, "squashed", "", "", "Tag to apply to squashed image")
+
+	squashCmd.MarkFlagRequired("original")
+	squashCmd.MarkFlagRequired("squashed")
+	return squashCmd
+}
+