Merge pull request #5191 from wplapper/cmd_rewrite_include

changelog/unreleased/issue-4278

@@ -0,0 +1,12 @@
+Enhancement: Support include filters in `rewrite` command
+
+The enhancement enables the standard include filter options
+      --iinclude pattern     same as --include pattern but ignores the casing of filenames
+      --iinclude-file file   same as --include-file but ignores casing of filenames in patterns
+  -i, --include pattern      include a pattern (can be specified multiple times)
+      --include-file file    read include patterns from a file (can be specified multiple times)
+
+The exclusion or inclusion of filter parameters is exclusive, as in other commands.
+
+https://github.com/restic/restic/issues/4278
+https://github.com/restic/restic/pull/5191

cmd/restic/cmd_repair_snapshots.go

@@ -151,7 +151,7 @@ func runRepairSnapshots(ctx context.Context, gopts global.Options, opts RepairOp
 			func(ctx context.Context, sn *data.Snapshot, uploader restic.BlobSaver) (restic.ID, *data.SnapshotSummary, error) {
 				id, err := rewriter.RewriteTree(ctx, repo, uploader, "/", *sn.Tree)
 				return id, nil, err
-			}, opts.DryRun, opts.Forget, nil, "repaired", printer)
+			}, opts.DryRun, opts.Forget, nil, "repaired", printer, false)
 		if err != nil {
 			return errors.Fatalf("unable to rewrite snapshot ID %q: %v", sn.ID().Str(), err)
 		}

cmd/restic/cmd_rewrite.go

@@ -30,6 +30,9 @@ The "rewrite" command excludes files from existing snapshots. It creates new
 snapshots containing the same data as the original ones, but without the files
 you specify to exclude. All metadata (time, host, tags) will be preserved.
 
+Alternatively you can use one of the --include variants to only include files
+in the new snapshot which you want to preserve.
+
 The snapshots to rewrite are specified using the --host, --tag and --path options,
 or by providing a list of snapshot IDs. Please note that specifying neither any of
 these options nor a snapshot ID will cause the command to rewrite all snapshots.
@@ -46,8 +49,8 @@ When rewrite is used with the --snapshot-summary option, a new snapshot is
 created containing statistics summary data. Only two fields in the summary will
 be non-zero: TotalFilesProcessed and TotalBytesProcessed.
 
-When rewrite is called with one of the --exclude options, TotalFilesProcessed
-and TotalBytesProcessed will be updated in the snapshot summary.
+When rewrite is called with one of the --exclude or --include options,
+TotalFilesProcessed and TotalBytesProcessed will be updated in the snapshot summary.
 
 EXIT STATUS
 ===========
@@ -109,6 +112,7 @@ type RewriteOptions struct {
 	Metadata snapshotMetadataArgs
 	data.SnapshotFilter
 	filter.ExcludePatternOptions
+	filter.IncludePatternOptions
 }
 
 func (opts *RewriteOptions) AddFlags(f *pflag.FlagSet) {
@@ -120,6 +124,7 @@ func (opts *RewriteOptions) AddFlags(f *pflag.FlagSet) {
 
 	initMultiSnapshotFilter(f, &opts.SnapshotFilter, true)
 	opts.ExcludePatternOptions.Add(f)
+	opts.IncludePatternOptions.Add(f)
 }
 
 // rewriteFilterFunc returns the filtered tree ID or an error. If a snapshot summary is returned, the snapshot will
@@ -136,33 +141,31 @@ func rewriteSnapshot(ctx context.Context, repo *repository.Repository, sn *data.
 		return false, err
 	}
 
+	includeByNameFuncs, err := opts.IncludePatternOptions.CollectPatterns(printer.E)
+	if err != nil {
+		return false, err
+	}
+
 	metadata, err := opts.Metadata.convert()
 
 	if err != nil {
 		return false, err
 	}
 
+	condInclude := len(includeByNameFuncs) > 0
+	condExclude := len(rejectByNameFuncs) > 0
 	var filter rewriteFilterFunc
 
-	if len(rejectByNameFuncs) > 0 || opts.SnapshotSummary {
-		selectByName := func(nodepath string) bool {
-			for _, reject := range rejectByNameFuncs {
-				if reject(nodepath) {
-					return false
-				}
-			}
-			return true
+	if condInclude || condExclude || opts.SnapshotSummary {
+		var rewriteNode walker.NodeRewriteFunc
+		var keepEmptyDirectoryFunc walker.NodeKeepEmptyDirectoryFunc
+		if condInclude {
+			rewriteNode, keepEmptyDirectoryFunc = gatherIncludeFilters(includeByNameFuncs, printer)
+		} else {
+			rewriteNode = gatherExcludeFilters(rejectByNameFuncs, printer)
 		}
 
-		rewriteNode := func(node *data.Node, path string) *data.Node {
-			if selectByName(path) {
-				return node
-			}
-			printer.P("excluding %s", path)
-			return nil
-		}
-
-		rewriter, querySize := walker.NewSnapshotSizeRewriter(rewriteNode)
+		rewriter, querySize := walker.NewSnapshotSizeRewriter(rewriteNode, keepEmptyDirectoryFunc)
 
 		filter = func(ctx context.Context, sn *data.Snapshot, uploader restic.BlobSaver) (restic.ID, *data.SnapshotSummary, error) {
 			id, err := rewriter.RewriteTree(ctx, repo, uploader, "/", *sn.Tree)
@@ -186,11 +189,12 @@ func rewriteSnapshot(ctx context.Context, repo *repository.Repository, sn *data.
 	}
 
 	return filterAndReplaceSnapshot(ctx, repo, sn,
-		filter, opts.DryRun, opts.Forget, metadata, "rewrite", printer)
+		filter, opts.DryRun, opts.Forget, metadata, "rewrite", printer, len(includeByNameFuncs) > 0)
 }
 
 func filterAndReplaceSnapshot(ctx context.Context, repo restic.Repository, sn *data.Snapshot,
-	filter rewriteFilterFunc, dryRun bool, forget bool, newMetadata *snapshotMetadata, addTag string, printer progress.Printer) (bool, error) {
+	filter rewriteFilterFunc, dryRun bool, forget bool, newMetadata *snapshotMetadata, addTag string, printer progress.Printer,
+	keepEmptySnapshot bool) (bool, error) {
 
 	var filteredTree restic.ID
 	var summary *data.SnapshotSummary
@@ -204,6 +208,10 @@ func filterAndReplaceSnapshot(ctx context.Context, repo restic.Repository, sn *d
 	}
 
 	if filteredTree.IsNull() {
+		if keepEmptySnapshot {
+			debug.Log("Snapshot %v not modified", sn)
+			return false, nil
+		}
 		if dryRun {
 			printer.P("would delete empty snapshot")
 		} else {
@@ -284,8 +292,12 @@ func filterAndReplaceSnapshot(ctx context.Context, repo restic.Repository, sn *d
 }
 
 func runRewrite(ctx context.Context, opts RewriteOptions, gopts global.Options, args []string, term ui.Terminal) error {
-	if !opts.SnapshotSummary && opts.ExcludePatternOptions.Empty() && opts.Metadata.empty() {
-		return errors.Fatal("Nothing to do: no excludes provided and no new metadata provided")
+	hasExcludes := !opts.ExcludePatternOptions.Empty()
+	hasIncludes := !opts.IncludePatternOptions.Empty()
+	if !opts.SnapshotSummary && !hasExcludes && !hasIncludes && opts.Metadata.empty() {
+		return errors.Fatal("Nothing to do: no excludes/includes provided and no new metadata provided")
+	} else if hasExcludes && hasIncludes {
+		return errors.Fatal("exclude and include patterns are mutually exclusive")
 	}
 
 	printer := ui.NewProgressPrinter(false, gopts.Verbosity, term)
@@ -348,3 +360,72 @@ func runRewrite(ctx context.Context, opts RewriteOptions, gopts global.Options,
 
 	return nil
 }
+
+func gatherIncludeFilters(includeByNameFuncs []filter.IncludeByNameFunc, printer progress.Printer) (rewriteNode walker.NodeRewriteFunc, keepEmptyDirectory walker.NodeKeepEmptyDirectoryFunc) {
+	inSelectByName := func(nodepath string, node *data.Node) bool {
+		for _, include := range includeByNameFuncs {
+			matched, childMayMatch := include(nodepath)
+			if node.Type == data.NodeTypeDir {
+				// include directories if they or some of their children may be included
+				if matched || childMayMatch {
+					return true
+				}
+			} else if matched {
+				return true
+			}
+		}
+		return false
+	}
+
+	rewriteNode = func(node *data.Node, path string) *data.Node {
+		if inSelectByName(path, node) {
+			if node.Type != data.NodeTypeDir {
+				printer.VV("including %q\n", path)
+			}
+			return node
+		}
+		return nil
+	}
+
+	inSelectByNameDir := func(nodepath string) bool {
+		for _, include := range includeByNameFuncs {
+			matched, _ := include(nodepath)
+			if matched {
+				return matched
+			}
+		}
+		return false
+	}
+
+	keepEmptyDirectory = func(path string) bool {
+		keep := inSelectByNameDir(path)
+		if keep {
+			printer.VV("including directory %q\n", path)
+		}
+		return keep
+	}
+
+	return rewriteNode, keepEmptyDirectory
+}
+
+func gatherExcludeFilters(excludeByNameFuncs []filter.RejectByNameFunc, printer progress.Printer) (rewriteNode walker.NodeRewriteFunc) {
+	exSelectByName := func(nodepath string) bool {
+		for _, reject := range excludeByNameFuncs {
+			if reject(nodepath) {
+				return false
+			}
+		}
+		return true
+	}
+
+	rewriteNode = func(node *data.Node, path string) *data.Node {
+		if exSelectByName(path) {
+			return node
+		}
+
+		printer.VV("excluding %q\n", path)
+		return nil
+	}
+
+	return rewriteNode
+}

cmd/restic/cmd_rewrite_integration_test.go

@@ -2,7 +2,9 @@ package main
 
 import (
 	"context"
+	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/restic/restic/internal/data"
@@ -27,6 +29,27 @@ func testRunRewriteExclude(t testing.TB, gopts global.Options, excludes []string
 	}))
 }
 
+func testRunRewriteWithOpts(t testing.TB, opts RewriteOptions, gopts global.Options, args []string) error {
+	rtest.OK(t, withTermStatus(t, gopts, func(ctx context.Context, gopts global.Options) error {
+		return runRewrite(context.TODO(), opts, gopts, args, gopts.Term)
+	}))
+	return nil
+}
+
+// testLsOutputContainsCount runs restic ls with the given options and asserts that
+// exactly expectedCount lines of the output contain substring.
+func testLsOutputContainsCount(t testing.TB, gopts global.Options, lsOpts LsOptions, lsArgs []string, substring string, expectedCount int) {
+	t.Helper()
+	out := testRunLsWithOpts(t, gopts, lsOpts, lsArgs)
+	count := 0
+	for _, line := range strings.Split(string(out), "\n") {
+		if strings.Contains(line, substring) {
+			count++
+		}
+	}
+	rtest.Assert(t, count == expectedCount, "expected %d lines containing %q, but got %d", expectedCount, substring, count)
+}
+
 func createBasicRewriteRepo(t testing.TB, env *testEnvironment) restic.ID {
 	testSetupBackupData(t, env)
 
@@ -39,6 +62,20 @@ func createBasicRewriteRepo(t testing.TB, env *testEnvironment) restic.ID {
 	return snapshotIDs[0]
 }
 
+func createBasicRewriteRepoWithEmptyDirectory(t testing.TB, env *testEnvironment) restic.ID {
+	testSetupBackupData(t, env)
+
+	// make an empty directory named "empty-directory"
+	rtest.OK(t, os.Mkdir(filepath.Join(env.testdata, "/0/tests", "empty-directory"), 0755))
+
+	// create backup
+	testRunBackup(t, filepath.Dir(env.testdata), []string{"testdata"}, BackupOptions{}, env.gopts)
+	snapshotIDs := testRunList(t, env.gopts, "snapshots")
+	rtest.Assert(t, len(snapshotIDs) == 1, "expected one snapshot, got %v", snapshotIDs)
+
+	return snapshotIDs[0]
+}
+
 func getSnapshot(t testing.TB, snapshotID restic.ID, env *testEnvironment) *data.Snapshot {
 	t.Helper()
 
@@ -195,3 +232,122 @@ func TestRewriteSnaphotSummary(t *testing.T) {
 	rtest.Equals(t, oldSummary.TotalBytesProcessed, newSn.Summary.TotalBytesProcessed, "unexpected TotalBytesProcessed value")
 	rtest.Equals(t, oldSummary.TotalFilesProcessed, newSn.Summary.TotalFilesProcessed, "unexpected TotalFilesProcessed value")
 }
+
+func TestRewriteInclude(t *testing.T) {
+	for _, tc := range []struct {
+		name                 string
+		opts                 RewriteOptions
+		lsSubstring          string
+		lsExpectedCount      int
+		summaryFilesExpected uint
+	}{
+		{"relative", RewriteOptions{
+			Forget:                true,
+			IncludePatternOptions: filter.IncludePatternOptions{Includes: []string{"*.txt"}},
+		}, ".txt", 2, 2},
+		{"absolute", RewriteOptions{
+			Forget: true,
+			// test that childMatches are working by only matching a subdirectory
+			IncludePatternOptions: filter.IncludePatternOptions{Includes: []string{"/testdata/0/for_cmd_ls"}},
+		}, "/testdata/0", 5, 3},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			env, cleanup := withTestEnvironment(t)
+			defer cleanup()
+			createBasicRewriteRepo(t, env)
+			snapshots := testListSnapshots(t, env.gopts, 1)
+
+			rtest.OK(t, testRunRewriteWithOpts(t, tc.opts, env.gopts, []string{"latest"}))
+
+			newSnapshots := testListSnapshots(t, env.gopts, 1)
+			rtest.Assert(t, snapshots[0] != newSnapshots[0], "snapshot id should have changed")
+
+			testLsOutputContainsCount(t, env.gopts, LsOptions{}, []string{"latest"}, tc.lsSubstring, tc.lsExpectedCount)
+			sn := testLoadSnapshot(t, env.gopts, newSnapshots[0])
+			rtest.Assert(t, sn.Summary != nil, "snapshot should have a summary attached")
+			rtest.Assert(t, sn.Summary.TotalFilesProcessed == tc.summaryFilesExpected,
+				"there should be %d files in the snapshot, but there are %d files", tc.summaryFilesExpected, sn.Summary.TotalFilesProcessed)
+		})
+	}
+}
+
+func TestRewriteExcludeFiles(t *testing.T) {
+	env, cleanup := withTestEnvironment(t)
+	defer cleanup()
+	createBasicRewriteRepo(t, env)
+	snapshots := testListSnapshots(t, env.gopts, 1)
+
+	// exclude txt files
+	err := testRunRewriteWithOpts(t,
+		RewriteOptions{
+			Forget:                true,
+			ExcludePatternOptions: filter.ExcludePatternOptions{Excludes: []string{"*.txt"}},
+		},
+		env.gopts,
+		[]string{"latest"})
+	rtest.OK(t, err)
+	newSnapshots := testListSnapshots(t, env.gopts, 1)
+	rtest.Assert(t, snapshots[0] != newSnapshots[0], "snapshot id should have changed")
+
+	testLsOutputContainsCount(t, env.gopts, LsOptions{}, []string{"latest"}, ".txt", 0)
+}
+
+func TestRewriteExcludeIncludeContradiction(t *testing.T) {
+	env, cleanup := withTestEnvironment(t)
+	defer cleanup()
+	testRunInit(t, env.gopts)
+
+	// test contradiction
+	err := withTermStatus(t, env.gopts, func(ctx context.Context, gopts global.Options) error {
+		return runRewrite(ctx,
+			RewriteOptions{
+				ExcludePatternOptions: filter.ExcludePatternOptions{Excludes: []string{"nonsense"}},
+				IncludePatternOptions: filter.IncludePatternOptions{Includes: []string{"not allowed"}},
+			},
+			gopts, []string{"quack"}, env.gopts.Term)
+	})
+	rtest.Assert(t, err != nil && strings.Contains(err.Error(), "exclude and include patterns are mutually exclusive"), `expected to fail command with message "exclude and include patterns are mutually exclusive"`)
+}
+
+func TestRewriteIncludeEmptyDirectory(t *testing.T) {
+	env, cleanup := withTestEnvironment(t)
+	defer cleanup()
+	snapIDEmpty := createBasicRewriteRepoWithEmptyDirectory(t, env)
+
+	// restic rewrite <snapshots[0]> -i empty-directory --forget
+	// exclude txt files
+	err := testRunRewriteWithOpts(t,
+		RewriteOptions{
+			Forget:                true,
+			IncludePatternOptions: filter.IncludePatternOptions{Includes: []string{"empty-directory"}},
+		},
+		env.gopts,
+		[]string{"latest"})
+	rtest.OK(t, err)
+	newSnapshots := testListSnapshots(t, env.gopts, 1)
+	rtest.Assert(t, snapIDEmpty != newSnapshots[0], "snapshot id should have changed")
+
+	testLsOutputContainsCount(t, env.gopts, LsOptions{}, []string{"latest"}, "empty-directory", 1)
+}
+
+// TestRewriteIncludeNothing makes sure when nothing is included, the original snapshot stays untouched
+func TestRewriteIncludeNothing(t *testing.T) {
+	env, cleanup := withTestEnvironment(t)
+	defer cleanup()
+	createBasicRewriteRepo(t, env)
+	snapsBefore := testListSnapshots(t, env.gopts, 1)
+
+	// restic rewrite latest -i nothing-whatsoever --forget
+	err := testRunRewriteWithOpts(t,
+		RewriteOptions{
+			Forget:                true,
+			IncludePatternOptions: filter.IncludePatternOptions{Includes: []string{"nothing-whatsoever"}},
+		},
+		env.gopts,
+		[]string{"latest"})
+	rtest.OK(t, err)
+
+	snapsAfter := testListSnapshots(t, env.gopts, 1)
+	rtest.Assert(t, snapsBefore[0] == snapsAfter[0], "snapshots should be identical but are %s and %s",
+		snapsBefore[0].Str(), snapsAfter[0].Str())
+}

doc/045_working_with_repos.rst

@@ -336,6 +336,13 @@ The options ``--exclude``, ``--exclude-file``, ``--iexclude`` and
 ``--iexclude-file`` are supported. They behave the same way as for the backup
 command, see :ref:`backup-excluding-files` for details.
 
+The options ``--include``, ``--include-file``, ``--iinclude`` and
+``--iinclude-file`` are supported as well.
+The ``--include`` variants allow you to reduce an existing snapshot or a set of snapshots
+to those files that you are really interested in. An example could be all pictures
+from a snapshot:
+``restic rewrite -r ... --iinclude "*.jpg" --iinclude "*.jpeg" --iinclude "*.png"``.
+
 It is possible to rewrite only a subset of snapshots by filtering them the same
 way as for the ``copy`` command, see :ref:`copy-filtering-snapshots`.
 

internal/data/tree.go

@@ -223,6 +223,11 @@ func (t *TreeWriter) Finalize(ctx context.Context) (restic.ID, error) {
 	return id, err
 }
 
+// Count returns the number of nodes in the tree
+func (t *TreeWriter) Count() int {
+	return t.builder.Count()
+}
+
 func SaveTree(ctx context.Context, saver restic.BlobSaver, nodes TreeNodeIterator) (restic.ID, error) {
 	treeWriter := NewTreeWriter(saver)
 	for item := range nodes {
@@ -238,8 +243,9 @@ func SaveTree(ctx context.Context, saver restic.BlobSaver, nodes TreeNodeIterato
 }
 
 type TreeJSONBuilder struct {
-	buf      bytes.Buffer
-	lastName string
+	buf        bytes.Buffer
+	lastName   string
+	countNodes int
 }
 
 func NewTreeJSONBuilder() *TreeJSONBuilder {
@@ -262,6 +268,7 @@ func (builder *TreeJSONBuilder) AddNode(node *Node) error {
 		return err
 	}
 	_, _ = builder.buf.Write(val)
+	builder.countNodes++
 	return nil
 }
 
@@ -275,6 +282,11 @@ func (builder *TreeJSONBuilder) Finalize() ([]byte, error) {
 	return buf, nil
 }
 
+// Count returns the number of nodes in the tree
+func (builder *TreeJSONBuilder) Count() int {
+	return builder.countNodes
+}
+
 func FindTreeDirectory(ctx context.Context, repo restic.BlobLoader, id *restic.ID, dir string) (*restic.ID, error) {
 	if id == nil {
 		return nil, errors.New("tree id is null")

internal/filter/include.go

@@ -25,6 +25,10 @@ func (opts *IncludePatternOptions) Add(f *pflag.FlagSet) {
 	f.StringArrayVar(&opts.InsensitiveIncludeFiles, "iinclude-file", nil, "same as --include-file but ignores casing of `file`names in patterns")
 }
 
+func (opts *IncludePatternOptions) Empty() bool {
+	return len(opts.Includes) == 0 && len(opts.InsensitiveIncludes) == 0 && len(opts.IncludeFiles) == 0 && len(opts.InsensitiveIncludeFiles) == 0
+}
+
 func (opts IncludePatternOptions) CollectPatterns(warnf func(msg string, args ...interface{})) ([]IncludeByNameFunc, error) {
 	var fs []IncludeByNameFunc
 	if len(opts.IncludeFiles) > 0 {

internal/walker/rewriter.go

@@ -13,6 +13,7 @@ import (
 type NodeRewriteFunc func(node *data.Node, path string) *data.Node
 type FailedTreeRewriteFunc func(nodeID restic.ID, path string, err error) (data.TreeNodeIterator, error)
 type QueryRewrittenSizeFunc func() SnapshotSize
+type NodeKeepEmptyDirectoryFunc func(path string) bool
 
 type SnapshotSize struct {
 	FileCount uint
@@ -21,7 +22,8 @@ type SnapshotSize struct {
 
 type RewriteOpts struct {
 	// return nil to remove the node
-	RewriteNode NodeRewriteFunc
+	RewriteNode        NodeRewriteFunc
+	KeepEmptyDirectory NodeKeepEmptyDirectoryFunc
 	// decide what to do with a tree that could not be loaded. Return nil to remove the node. By default the load error is returned which causes the operation to fail.
 	RewriteFailedTree FailedTreeRewriteFunc
 
@@ -56,10 +58,15 @@ func NewTreeRewriter(opts RewriteOpts) *TreeRewriter {
 			return nil, err
 		}
 	}
+	if rw.opts.KeepEmptyDirectory == nil {
+		rw.opts.KeepEmptyDirectory = func(_ string) bool {
+			return true
+		}
+	}
 	return rw
 }
 
-func NewSnapshotSizeRewriter(rewriteNode NodeRewriteFunc) (*TreeRewriter, QueryRewrittenSizeFunc) {
+func NewSnapshotSizeRewriter(rewriteNode NodeRewriteFunc, keepEmptyDirecoryFilter NodeKeepEmptyDirectoryFunc) (*TreeRewriter, QueryRewrittenSizeFunc) {
 	var count uint
 	var size uint64
 
@@ -72,7 +79,8 @@ func NewSnapshotSizeRewriter(rewriteNode NodeRewriteFunc) (*TreeRewriter, QueryR
 			}
 			return node
 		},
-		DisableNodeCache: true,
+		DisableNodeCache:   true,
+		KeepEmptyDirectory: keepEmptyDirecoryFilter,
 	})
 
 	ss := func() SnapshotSize {
@@ -159,6 +167,8 @@ func (t *TreeRewriter) RewriteTree(ctx context.Context, loader restic.BlobLoader
 		newID, err := t.RewriteTree(ctx, loader, saver, path, subtree)
 		if err != nil {
 			return restic.ID{}, err
+		} else if err == nil && newID.IsNull() {
+			continue
 		}
 		node.Subtree = &newID
 		err = tb.AddNode(node)
@@ -171,6 +181,9 @@ func (t *TreeRewriter) RewriteTree(ctx context.Context, loader restic.BlobLoader
 	if err != nil {
 		return restic.ID{}, err
 	}
+	if tb.Count() == 0 && !t.opts.KeepEmptyDirectory(nodepath) {
+		return restic.ID{}, nil
+	}
 
 	if t.replaces != nil {
 		t.replaces[nodeID] = newTreeID

internal/walker/rewriter_test.go

@@ -306,7 +306,7 @@ func TestSnapshotSizeQuery(t *testing.T) {
 			}
 			return node
 		}
-		rewriter, querySize := NewSnapshotSizeRewriter(rewriteNode)
+		rewriter, querySize := NewSnapshotSizeRewriter(rewriteNode, nil)
 		newRoot, err := rewriter.RewriteTree(ctx, modrepo, modrepo, "/", root)
 		if err != nil {
 			t.Error(err)
@@ -329,6 +329,74 @@ func TestSnapshotSizeQuery(t *testing.T) {
 
 }
 
+func TestRewriterKeepEmptyDirectory(t *testing.T) {
+	var paths []string
+	tests := []struct {
+		name      string
+		keepEmpty NodeKeepEmptyDirectoryFunc
+		assert    func(t *testing.T, newRoot restic.ID)
+	}{
+		{
+			name:      "Keep",
+			keepEmpty: func(string) bool { return true },
+			assert: func(t *testing.T, newRoot restic.ID) {
+				_, expRoot := BuildTreeMap(TestTree{"empty": TestTree{}})
+				test.Assert(t, newRoot == expRoot, "expected empty dir kept")
+			},
+		},
+		{
+			name:      "Drop subdir only",
+			keepEmpty: func(p string) bool { return p != "/empty" },
+			assert: func(t *testing.T, newRoot restic.ID) {
+				_, expRoot := BuildTreeMap(TestTree{})
+				test.Assert(t, newRoot == expRoot, "expected empty root")
+			},
+		},
+		{
+			name:      "Drop all",
+			keepEmpty: func(string) bool { return false },
+			assert: func(t *testing.T, newRoot restic.ID) {
+				test.Assert(t, newRoot.IsNull(), "expected null root")
+			},
+		},
+		{
+			name: "Paths",
+			keepEmpty: func(p string) bool {
+				paths = append(paths, p)
+				return p != "/empty"
+			},
+			assert: func(t *testing.T, newRoot restic.ID) {
+				test.Assert(t, len(paths) >= 2, "expected at least two KeepEmptyDirectory calls")
+				var hasRoot, hasEmpty bool
+				for _, p := range paths {
+					if p == "/" {
+						hasRoot = true
+					}
+					if p == "/empty" {
+						hasEmpty = true
+					}
+				}
+				test.Assert(t, hasRoot && hasEmpty, "expected paths \"/\" and \"/empty\", got %v", paths)
+			},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+
+			repo, root := BuildTreeMap(TestTree{"empty": TestTree{}})
+			modrepo := data.TestWritableTreeMap{TestTreeMap: repo}
+
+			rw := NewTreeRewriter(RewriteOpts{KeepEmptyDirectory: tc.keepEmpty})
+			newRoot, err := rw.RewriteTree(ctx, modrepo, modrepo, "/", root)
+			test.OK(t, err)
+			tc.assert(t, newRoot)
+		})
+	}
+}
+
 func TestRewriterFailOnUnknownFields(t *testing.T) {
 	tm := data.TestWritableTreeMap{TestTreeMap: data.TestTreeMap{}}
 	node := []byte(`{"nodes":[{"name":"subfile","type":"file","mtime":"0001-01-01T00:00:00Z","atime":"0001-01-01T00:00:00Z","ctime":"0001-01-01T00:00:00Z","uid":0,"gid":0,"content":null,"unknown_field":42}]}`)