dump: add --compress-zip flag to compress zip archives

changelog/unreleased/pull-5054

@@ -0,0 +1,10 @@
+Enhancement: Add `--compress` flag to `dump` command to compress archive
+
+Restic did not compress the archives that was created by using the
+`dump` command. It now allows to save some disk space when exporting
+archives by adding a `--compress` flag. The DEFLATE algorithm is used
+for "zip" archives, and the gzip algorithm for "tar" archives,
+resulting in a .tar.gz or .tgz file. Not compressing the archive
+is still the default.
+
+https://github.com/restic/restic/pull/5054

cmd/restic/cmd_dump.go

@@ -50,8 +50,9 @@ Exit status is 12 if the password is incorrect.
 // DumpOptions collects all options for the dump command.
 type DumpOptions struct {
 	restic.SnapshotFilter
-	Archive string
-	Target  string
+	Archive  string
+	Target   string
+	Compress bool
 }
 
 var dumpOptions DumpOptions
@@ -63,6 +64,7 @@ func init() {
 	initSingleSnapshotFilter(flags, &dumpOptions.SnapshotFilter)
 	flags.StringVarP(&dumpOptions.Archive, "archive", "a", "tar", "set archive `format` as \"tar\" or \"zip\"")
 	flags.StringVarP(&dumpOptions.Target, "target", "t", "", "write the output to target `path`")
+	flags.BoolVarP(&dumpOptions.Compress, "compress", "c", false, "compress archive contents. When enabled, the DEFLATE algorithm is applied for \"zip\" archives, and the gzip algorithm for \"tar\" archives, resulting in a .tar.gz or .tgz file. (default: false)")
 }
 
 func splitPath(p string) []string {
@@ -187,7 +189,7 @@ func runDump(ctx context.Context, opts DumpOptions, gopts GlobalOptions, args []
 		canWriteArchiveFunc = func() error { return nil }
 	}
 
-	d := dump.New(opts.Archive, repo, outputFileWriter)
+	d := dump.New(opts.Archive, opts.Compress, repo, outputFileWriter)
 	err = printFromTree(ctx, tree, repo, "/", splittedPath, d, canWriteArchiveFunc)
 	if err != nil {
 		return errors.Fatalf("cannot dump file: %v", err)

internal/dump/common.go

@@ -15,18 +15,20 @@ import (
 // A Dumper writes trees and files from a repository to a Writer
 // in an archive format.
 type Dumper struct {
-	cache  *bloblru.Cache
-	format string
-	repo   restic.Loader
-	w      io.Writer
+	cache    *bloblru.Cache
+	format   string
+	repo     restic.Loader
+	w        io.Writer
+	compress bool
 }
 
-func New(format string, repo restic.Loader, w io.Writer) *Dumper {
+func New(format string, compress bool, repo restic.Loader, w io.Writer) *Dumper {
 	return &Dumper{
-		cache:  bloblru.New(64 << 20),
-		format: format,
-		repo:   repo,
-		w:      w,
+		cache:    bloblru.New(64 << 20),
+		format:   format,
+		repo:     repo,
+		w:        w,
+		compress: compress,
 	}
 }
 

internal/dump/common_test.go

@@ -23,7 +23,7 @@ func prepareTempdirRepoSrc(t testing.TB, src archiver.TestDir) (string, restic.R
 
 type CheckDump func(t *testing.T, testDir string, testDump *bytes.Buffer) error
 
-func WriteTest(t *testing.T, format string, cd CheckDump) {
+func WriteTest(t *testing.T, format string, compress bool, cd CheckDump) {
 	tests := []struct {
 		name   string
 		args   archiver.TestDir
@@ -85,7 +85,7 @@ func WriteTest(t *testing.T, format string, cd CheckDump) {
 			rtest.OK(t, err)
 
 			dst := &bytes.Buffer{}
-			d := New(format, repo, dst)
+			d := New(format, compress, repo, dst)
 			if err := d.DumpTree(ctx, tree, tt.target); err != nil {
 				t.Fatalf("Dumper.Run error = %v", err)
 			}

internal/dump/tar.go

@@ -2,6 +2,7 @@ package dump
 
 import (
 	"archive/tar"
+	"compress/gzip"
 	"context"
 	"fmt"
 	"os"
@@ -13,12 +14,22 @@ import (
 )
 
 func (d *Dumper) dumpTar(ctx context.Context, ch <-chan *restic.Node) (err error) {
-	w := tar.NewWriter(d.w)
+	outer := d.w
+
+	if d.compress {
+		outer = gzip.NewWriter(outer)
+	}
+	w := tar.NewWriter(outer)
 
 	defer func() {
 		if err == nil {
 			err = w.Close()
 			err = errors.Wrap(err, "Close")
+
+			if gz, ok := outer.(*gzip.Writer); ok {
+				err = gz.Close()
+				err = errors.Wrap(err, "Close")
+			}
 		}
 	}()
 

internal/dump/tar_test.go

@@ -18,7 +18,8 @@ import (
 )
 
 func TestWriteTar(t *testing.T) {
-	WriteTest(t, "tar", checkTar)
+	WriteTest(t, "tar", false, checkTar)
+	WriteTest(t, "tar", true, checkTar)
 }
 
 func checkTar(t *testing.T, testDir string, srcTar *bytes.Buffer) error {

internal/dump/zip.go

@@ -40,6 +40,10 @@ func (d *Dumper) dumpNodeZip(ctx context.Context, node *restic.Node, zw *zip.Wri
 	}
 	header.SetMode(node.Mode)
 
+	if d.compress {
+		header.Method = zip.Deflate
+	}
+
 	if node.Type == restic.NodeTypeDir {
 		header.Name += "/"
 	}

internal/dump/zip_test.go

@@ -12,7 +12,8 @@ import (
 )
 
 func TestWriteZip(t *testing.T) {
-	WriteTest(t, "zip", checkZip)
+	WriteTest(t, "zip", true, checkZip)
+	WriteTest(t, "zip", false, checkZip)
 }
 
 func readZipFile(f *zip.File) ([]byte, error) {